Add a Molecule scenario for mautrix-whatsapp, and a shared playbook context

The second scenario, chosen to be a bridge rather than another HTTP
component: bridges are roughly 40 of the 70 roles here, and validating the
shape on role two is cheaper than discovering it on role forty. It found
two things the first role could not.

Bridges read a whole family of variables from outside themselves -
matrix_bridges_relay_enabled, _encryption_enabled, _encryption_default,
_msc4190_enabled, _self_sign_enabled, plus matrix_admin - all defined in
matrix-base. Since every bridge reads them, they belong in shared context
rather than in each bridge's scenario: molecule-shared/playbook-context.yml
now carries them along with the identity and path variables the first
scenario had inline. Note it is loaded through vars_files, which outranks
inventory group_vars, so it is authoritative; a scenario that wants to prove
one of these reaches the rendered configuration should say so explicitly.

Appservices call /whoami while starting and refuse to run if the id returned
is not the bot user they were configured as - mautrix-whatsapp exits 17 with
"Unexpected user ID in whoami call". The shared stub now takes the id it
should claim to be. Expect every bridge and bot to need this.

What the scenario proves: the bridge starts and stays up, opens its
appservice port, its rendered config and appservice registration carry the
scenario's tokens and bot user, it created its sqlite database under the
role's data path as the role's uid, and it runs the version the role pins.
It does not bridge anything and never will.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

roles/custom/matrix-alertmanager-receiver/molecule/default/converge.yml

@@ -11,6 +11,8 @@
 - name: Include roles for matrix-alertmanager-receiver Molecule tests
   hosts: all
   become: true
+  vars_files:
+    - "{{ lookup('env', 'MOLECULE_PROJECT_DIRECTORY') }}/../../../molecule-shared/playbook-context.yml"
   gather_facts: true
   tasks:
     - name: Include roles for matrix-alertmanager-receiver Molecule tests

roles/custom/matrix-alertmanager-receiver/molecule/default/molecule.yml

@@ -27,18 +27,6 @@ provisioner:
   inventory:
     group_vars:
       all:
-        # This role lives inside the playbook, so the variables the playbook
-        # would normally supply from `matrix-base` and from group_vars have to
-        # be provided here instead. These are the ones the role actually reads.
-        matrix_base_data_path: /matrix
-        matrix_domain: molecule.local
-        matrix_user_name: matrix
-        matrix_group_name: matrix
-        # Deliberately not 1000: the ubuntu2604 image already has a user there,
-        # so a distinct id proves the role used the one it was given.
-        matrix_user_uid: 1234
-        matrix_user_gid: 1234
-
         matrix_alertmanager_receiver_hostname: alertmanager-receiver.molecule.local
         matrix_alertmanager_receiver_path_prefix: /
         matrix_alertmanager_receiver_container_network: matrix-alertmanager-receiver-molecule

roles/custom/matrix-alertmanager-receiver/molecule/default/prepare.yml

@@ -8,6 +8,7 @@
   become: true
   vars_files:
     - "{{ lookup('env', 'MOLECULE_PROJECT_DIRECTORY') }}/../../../molecule-shared/vars.yml"
+    - "{{ lookup('env', 'MOLECULE_PROJECT_DIRECTORY') }}/../../../molecule-shared/playbook-context.yml"
   gather_facts: true
   tasks:
     - name: Ensure apt cache is updated

roles/custom/matrix-alertmanager-receiver/molecule/default/verify.yml

@@ -8,6 +8,7 @@
   become: true
   vars_files:
     - "{{ lookup('env', 'MOLECULE_PROJECT_DIRECTORY') }}/../../../molecule-shared/vars.yml"
+    - "{{ lookup('env', 'MOLECULE_PROJECT_DIRECTORY') }}/../../../molecule-shared/playbook-context.yml"
   gather_facts: false
 
   tasks: