Move roles/matrix* to roles/custom/matrix*

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.

roles/custom/matrix-postgres/tasks/import_postgres.yml

@@ -0,0 +1,114 @@
+---
+
+# Pre-checks
+
+- name: Fail if Postgres not enabled
+  ansible.builtin.fail:
+    msg: "Postgres via the matrix-postgres role is not enabled (`matrix_postgres_enabled`). Cannot import."
+  when: "not matrix_postgres_enabled | bool"
+
+- name: Fail if playbook called incorrectly
+  ansible.builtin.fail:
+    msg: "The `server_path_postgres_dump` variable needs to be provided to this playbook, via --extra-vars"
+  when: "server_path_postgres_dump is not defined or server_path_postgres_dump.startswith('<')"
+
+- name: Check if the provided Postgres dump file exists
+  ansible.builtin.stat:
+    path: "{{ server_path_postgres_dump }}"
+  register: result_server_path_postgres_dump_stat
+
+- name: Fail if provided Postgres dump file doesn't exists
+  ansible.builtin.fail:
+    msg: "File cannot be found on the server at {{ server_path_postgres_dump }}"
+  when: "not result_server_path_postgres_dump_stat.stat.exists"
+
+
+# Defaults
+
+- name: Set postgres_start_wait_time, if not provided
+  ansible.builtin.set_fact:
+    postgres_start_wait_time: 15
+  when: "postgres_start_wait_time | default('') == ''"
+
+- name: Set postgres_import_wait_time, if not provided
+  ansible.builtin.set_fact:
+    postgres_import_wait_time: "{{ 7 * 86400 }}"
+  when: "postgres_import_wait_time | default('') == ''"
+
+# By default, we connect and import into the main (`matrix`) database.
+# Single-database dumps for Synapse may wish to import into `synapse` instead.
+- name: Set postgres_default_import_database, if not provided
+  ansible.builtin.set_fact:
+    postgres_default_import_database: "{{ matrix_postgres_db_name }}"
+  when: "postgres_default_import_database | default('') == ''"
+
+# Actual import work
+
+- name: Ensure matrix-postgres is started
+  ansible.builtin.service:
+    name: matrix-postgres
+    state: started
+    daemon_reload: true
+  register: matrix_postgres_import_start_result
+
+- name: Wait a bit, so that Postgres can start
+  when: matrix_postgres_import_start_result.changed | bool
+  ansible.builtin.wait_for:
+    timeout: "{{ postgres_start_wait_time }}"
+  delegate_to: 127.0.0.1
+  become: false
+
+- ansible.builtin.import_tasks: tasks/detect_existing_postgres_version.yml
+
+- name: Abort, if no existing Postgres version detected
+  ansible.builtin.fail:
+    msg: "Could not find existing Postgres installation"
+  when: "not matrix_postgres_detected_existing | bool"
+
+# Starting the database container had automatically created the default
+# role (`matrix_postgres_connection_username`) and database (`matrix_postgres_db_name`).
+# The dump most likely contains those same entries and would try to re-create them, leading to errors.
+# We need to skip over those lines.
+- name: Generate Postgres database import command
+  ansible.builtin.set_fact:
+    matrix_postgres_import_command: >-
+      {{ matrix_host_command_docker }} run --rm --name matrix-postgres-import
+      --log-driver=none
+      --user={{ matrix_user_uid }}:{{ matrix_user_gid }}
+      --cap-drop=ALL
+      --network={{ matrix_docker_network }}
+      --env-file={{ matrix_postgres_base_path }}/env-postgres-psql
+      --mount type=bind,src={{ server_path_postgres_dump }},dst=/{{ server_path_postgres_dump | basename }},ro
+      --entrypoint=/bin/sh
+      {{ matrix_postgres_docker_image_latest }}
+      -c "cat /{{ server_path_postgres_dump | basename }} |
+      {{ 'gunzip |' if server_path_postgres_dump.endswith('.gz') else '' }}
+      grep -vE '{{ matrix_postgres_import_roles_ignore_regex }}' |
+      grep -vE '{{ matrix_postgres_import_databases_ignore_regex }}' |
+      psql -v ON_ERROR_STOP=1 -h matrix-postgres --dbname={{ postgres_default_import_database }}"
+  tags:
+    - skip_ansible_lint
+
+# This is a hack.
+# See: https://ansibledaily.com/print-to-standard-output-without-escaping/
+#
+# We want to run `debug: msg=".."`, but that dumps it as JSON and escapes double quotes within it,
+# which ruins the command (`matrix_postgres_import_command`)
+- name: Note about Postgres importing alternative
+  ansible.builtin.set_fact:
+    dummy: true
+  with_items:
+    - >-
+        Importing Postgres database using the following command: `{{ matrix_postgres_import_command }}`.
+        If this crashes, you can stop Postgres (`systemctl stop matrix-postgres`),
+        delete its existing data (`rm -rf {{ matrix_postgres_data_path }}/*`), start it again (`systemctl start matrix-postgres`)
+        and manually run the above import command directly on the server.
+
+- name: Perform Postgres database import
+  ansible.builtin.command:
+    cmd: "{{ matrix_postgres_import_command }}"
+  async: "{{ postgres_import_wait_time }}"
+  poll: 10
+  register: matrix_postgres_import_postgres_command_result
+  failed_when: not matrix_postgres_import_postgres_command_result.finished or matrix_postgres_import_postgres_command_result.rc != 0
+  changed_when: matrix_postgres_import_postgres_command_result.finished and matrix_postgres_import_postgres_command_result.rc == 0