Add support for Meowlnir

Meowlnir (https://github.com/maunium/meowlnir) is a Matrix moderation
bot which speaks the same policy-list protocol as Mjolnir and Draupnir,
but runs as an appservice and can override individual policies coming
from ban lists you do not control.

Bots and their management rooms live only in Meowlnir's own database —
nothing in its configuration file can declare one — so the role
provisions them through the management API from a declarative roster
(matrix_bot_meowlnir_bots_custom), applied under the
ensure-matrix-users-created tag. Management rooms may be declared or
created for you; bots and rooms no longer declared get pruned.

Wrapper scripts for driving the management API by hand are installed
to /matrix/meowlnir/bin.

Meowlnir re-runs its configuration upgrader in memory on every start,
so a literal `generate` value yields a new secret per restart. All
secrets are therefore rendered explicitly, validation rejects
`generate`, and the configuration directory is mounted read-only.

Draupnir and Meowlnir both want synapse-http-antispam, which the
playbook wires up to a single consumer. The wiring prefers Draupnir,
and both roles fail the run when each claims it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

roles/custom/matrix-bot-meowlnir/templates/bin/meowlnir-api.j2

@@ -0,0 +1,55 @@
+#!/bin/sh
+# Talks to Meowlnir's management API.
+#
+# The API is not published outside the container network, so requests are made from inside the container, which ships with curl.
+# The management secret is read out of the live configuration file, so that it lives in exactly one place.
+#
+# Usage: meowlnir-api <METHOD> <PATH> [JSON_BODY]
+# Example: meowlnir-api GET /_meowlnir/v1/bots
+#
+# Prints the response body, followed by the HTTP status code on its own final line.
+
+set -eu
+
+CONFIG_FILE='{{ matrix_bot_meowlnir_config_path }}/config.yaml'
+CONTAINER_NAME='matrix-bot-meowlnir'
+API_BASE='http://localhost:{{ matrix_bot_meowlnir_config_meowlnir_port }}'
+
+if [ $# -lt 2 ]; then
+	echo "Usage: $(basename "$0") <METHOD> <PATH> [JSON_BODY]" >&2
+	echo "Example: $(basename "$0") GET /_meowlnir/v1/bots" >&2
+	exit 2
+fi
+
+method="$1"
+api_path="$2"
+body="${3:-}"
+
+# The configuration file is generated by Ansible, so its layout is predictable.
+secret="$(awk '$1 == "management_secret:" { print $2; exit }' "$CONFIG_FILE" | sed 's/^"//; s/"$//')"
+
+if [ -z "$secret" ]; then
+	echo "Could not read management_secret from $CONFIG_FILE" >&2
+	exit 1
+fi
+
+if [ "$secret" = 'disable' ]; then
+	echo "Meowlnir's management API is disabled (management_secret is set to 'disable')" >&2
+	exit 1
+fi
+
+if [ -n "$body" ]; then
+	exec {{ devture_systemd_docker_base_host_command_docker }} exec "$CONTAINER_NAME" \
+		curl -sS -X "$method" \
+		-H "Authorization: Bearer $secret" \
+		-H 'Content-Type: application/json' \
+		-d "$body" \
+		-w '\n%{http_code}' \
+		"$API_BASE$api_path"
+fi
+
+exec {{ devture_systemd_docker_base_host_command_docker }} exec "$CONTAINER_NAME" \
+	curl -sS -X "$method" \
+	-H "Authorization: Bearer $secret" \
+	-w '\n%{http_code}' \
+	"$API_BASE$api_path"

roles/custom/matrix-bot-meowlnir/templates/bin/meowlnir-api.j2.license

@@ -0,0 +1,3 @@
+SPDX-FileCopyrightText: 2026 Slavi Pantaleev
+
+SPDX-License-Identifier: AGPL-3.0-or-later

roles/custom/matrix-bot-meowlnir/templates/bin/meowlnir-bots.j2

@@ -0,0 +1,21 @@
+#!/bin/sh
+# Shows the bots Meowlnir knows about, together with their management rooms, protected rooms and watched policy lists.
+#
+# Usage: meowlnir-bots
+
+set -eu
+
+BIN_PATH='{{ matrix_bot_meowlnir_bin_path }}'
+CONTAINER_NAME='matrix-bot-meowlnir'
+
+response="$("$BIN_PATH/meowlnir-api" GET /_meowlnir/v1/bots)"
+status="$(printf '%s\n' "$response" | tail -n 1)"
+body="$(printf '%s\n' "$response" | sed '$d')"
+
+if [ "$status" != '200' ]; then
+	echo "Meowlnir answered with HTTP $status:" >&2
+	echo "$body" >&2
+	exit 1
+fi
+
+printf '%s\n' "$body" | {{ devture_systemd_docker_base_host_command_docker }} exec -i "$CONTAINER_NAME" jq .

roles/custom/matrix-bot-meowlnir/templates/bin/meowlnir-bots.j2.license

@@ -0,0 +1,3 @@
+SPDX-FileCopyrightText: 2026 Slavi Pantaleev
+
+SPDX-License-Identifier: AGPL-3.0-or-later

roles/custom/matrix-bot-meowlnir/templates/bin/meowlnir-create-management-room.j2

@@ -0,0 +1,90 @@
+#!/bin/sh
+# Creates a management room for a Meowlnir bot, with the given users able to command the bot there.
+#
+# The room is created by the bot itself, impersonated through the appservice token, so no human account's credentials are needed.
+#
+# The `trusted_private_chat` preset is what gives the invited users their standing, and it does the right thing on both old and new room versions: on rooms supporting MSC4289 every invitee becomes an additional creator, and on older ones each is given power level 100.
+# Either way there is nothing for us to adjust afterwards.
+#
+# Usage: meowlnir-create-management-room <bot_localpart> <initial_manager_mxid>...
+#
+# Prints the created room's ID on success.
+
+set -eu
+
+CONFIG_FILE='{{ matrix_bot_meowlnir_config_path }}/config.yaml'
+CONTAINER_NAME='matrix-bot-meowlnir'
+HOMESERVER_ADDRESS='{{ matrix_bot_meowlnir_config_homeserver_address }}'
+HOMESERVER_DOMAIN='{{ matrix_bot_meowlnir_config_homeserver_domain }}'
+ROOM_NAME='{{ matrix_bot_meowlnir_management_room_name }}'
+ROOM_TOPIC='{{ matrix_bot_meowlnir_management_room_topic | trim }}'
+ENCRYPTED='{{ 'true' if matrix_bot_meowlnir_config_encryption_enable else 'false' }}'
+
+if [ $# -lt 2 ]; then
+	echo "Usage: $(basename "$0") <bot_localpart> <initial_manager_mxid>..." >&2
+	exit 2
+fi
+
+bot_localpart="$1"
+shift
+bot_mxid="@$bot_localpart:$HOMESERVER_DOMAIN"
+
+as_token="$(awk '$1 == "as_token:" { print $2; exit }' "$CONFIG_FILE" | sed 's/^"//; s/"$//')"
+
+if [ -z "$as_token" ]; then
+	echo "Could not read as_token from $CONFIG_FILE" >&2
+	exit 1
+fi
+
+urlencode() {
+	printf '%s' "$1" | sed 's/%/%25/g; s/!/%21/g; s/:/%3A/g; s/@/%40/g; s/\$/%24/g; s/\//%2F/g'
+}
+
+jq_run() {
+	{{ devture_systemd_docker_base_host_command_docker }} exec -i "$CONTAINER_NAME" jq "$@"
+}
+
+if [ "$ENCRYPTED" = 'true' ]; then
+	initial_state='[{"type": "m.room.encryption", "state_key": "", "content": {"algorithm": "m.megolm.v1.aes-sha2"}}]'
+else
+	initial_state='[]'
+fi
+
+# Matrix user IDs cannot contain newlines, so splitting on them is safe here.
+invitees="$(printf '%s\n' "$@" | jq_run -R -s 'split("\n") | map(select(length > 0))')"
+
+create_body="$(jq_run -n \
+	--arg name "$ROOM_NAME" \
+	--arg topic "$ROOM_TOPIC" \
+	--argjson invitees "$invitees" \
+	--argjson initial_state "$initial_state" \
+	'{preset: "trusted_private_chat", name: $name, topic: $topic, invite: $invitees, initial_state: $initial_state}')"
+
+user_id_param="$(urlencode "$bot_mxid")"
+
+# Runs curl inside the container, because the homeserver is only reachable over the container network.
+# Prints the body, with the HTTP status code on the final line.
+response="$({{ devture_systemd_docker_base_host_command_docker }} exec "$CONTAINER_NAME" \
+	curl -sS -X POST \
+	-H "Authorization: Bearer $as_token" \
+	-H 'Content-Type: application/json' \
+	-d "$create_body" \
+	-w '\n%{http_code}' \
+	"$HOMESERVER_ADDRESS/_matrix/client/v3/createRoom?user_id=$user_id_param")"
+
+status="$(printf '%s\n' "$response" | tail -n 1)"
+
+if [ "$status" != '200' ]; then
+	echo "Creating the management room failed with HTTP $status:" >&2
+	printf '%s\n' "$response" | sed '$d' >&2
+	exit 1
+fi
+
+room_id="$(printf '%s\n' "$response" | sed '$d' | jq_run -r '.room_id')"
+
+if [ -z "$room_id" ] || [ "$room_id" = 'null' ]; then
+	echo 'The homeserver did not return a room ID' >&2
+	exit 1
+fi
+
+printf '%s\n' "$room_id"

roles/custom/matrix-bot-meowlnir/templates/bin/meowlnir-create-management-room.j2.license

@@ -0,0 +1,3 @@
+SPDX-FileCopyrightText: 2026 Slavi Pantaleev
+
+SPDX-License-Identifier: AGPL-3.0-or-later