Add matrix-appservice-kakaotalk support

Adds support for: https://src.miscworks.net/fair/matrix-appservice-kakaotalk

This is pretty similar to
https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1977
which just appeared, but has mostly been done independently.

I've taken some inspiration and did some fixups based on that PR.
Thanks to https://github.com/hnarjis for taking the time to contribute!

Notable differences between this branch compared to that PR:

- better naming and documentation around the "configuration" variables
- no unnecessary (5 sec.) intentional delay when starting `matrix-appservice-kakaotalk-node.service`
- stores configuration in `config/`, not in `data/`
- passes configuration as read-only and starts the bridge with (`--no-update`) to ensure no changes are made to it
- starts containers more securely - with `matrix:matrix` user:group (not `root`) and
  reduced capabilities (`--cap-drop=ALL`)
- uses `tcp` for communication between the "node" and the appservice (simpler than sharing unix sockets)
- `registration.yaml` which is closer to the one generated by `matrix-appservice-kakaotalk` (no `de.sorunome.msc2409.push_ephemeral` stuff, etc.)
- `registration.yaml` which is more customizable (customizable bot username and prefix for puppets - see `matrix_appservice_kakaotalk_appservice_bot_username` and `matrix_appservice_kakaotalk_user_prefix`)
- less fragile and more extensible bridge permissions configuration via `matrix_appservice_kakaotalk_bridge_permissions`. Doing `{% if matrix_admin %}` in the bridge configuration sometimes causes syntax problems (I hit some myself) and is not ideal. Other bridges should be redone as well.
- configurable command prefix for the bridge, instead of hardcoding `!kt` (see `matrix_appservice_kakaotalk_command_prefix`)
- logging that is more consistent with the rest of the playbook (console / journald only, no logging to files), as well as configurable log level (via `matrix_appservice_kakaotalk_logging_level`)
- somewhat more detailed documentation (`docs/configuring-playbook-bridge-appservice-kakaotalk.md`)
- removed some dead code (data relocation tasks from `tasks/setup_install.yml`, as well as likely unnecessary SQLite -> Postgres migration)

group_vars/matrix_servers

@@ -213,6 +213,43 @@ matrix_appservice_irc_database_password: "{{ '%s' | format(matrix_homeserver_gen
 #
 ######################################################################
 
+######################################################################
+#
+# matrix-bridge-appservice-kakaotalk
+#
+######################################################################
+
+# We don't enable bridges by default.
+matrix_appservice_kakaotalk_enabled: false
+
+matrix_appservice_kakaotalk_systemd_required_services_list: |
+  {{
+    ['docker.service']
+    +
+    ['matrix-appservice-kakaotalk-node.service']
+    +
+    ['matrix-' + matrix_homeserver_implementation + '.service']
+    +
+    (['matrix-nginx-proxy.service'] if matrix_nginx_proxy_enabled else [])
+    +
+    (['matrix-postgres.service'] if matrix_postgres_enabled else [])
+  }}
+
+matrix_appservice_kakaotalk_appservice_token: "{{ '%s' | format(matrix_homeserver_generic_secret_key) | password_hash('sha512', 'as.kakao.hs') | to_uuid }}"
+
+matrix_appservice_kakaotalk_homeserver_token: "{{ '%s' | format(matrix_homeserver_generic_secret_key) | password_hash('sha512', 'as.kakao.hs') | to_uuid }}"
+
+matrix_appservice_kakaotalk_login_shared_secret: "{{ matrix_synapse_ext_password_provider_shared_secret_auth_shared_secret if matrix_synapse_ext_password_provider_shared_secret_auth_enabled else '' }}"
+
+matrix_appservice_kakaotalk_database_engine: "{{ 'postgres' if matrix_postgres_enabled else 'sqlite' }}"
+matrix_appservice_kakaotalk_database_password: "{{ '%s' | format(matrix_homeserver_generic_secret_key) | password_hash('sha512', 'as.kakao.db') | to_uuid }}"
+
+######################################################################
+#
+# /matrix-bridge-appservice-kakaotalk
+#
+######################################################################
+
 
 ######################################################################
 #
@@ -1811,6 +1848,12 @@ matrix_postgres_additional_databases: |
       'password': matrix_appservice_irc_database_password,
     }] if (matrix_appservice_irc_enabled and matrix_appservice_irc_database_engine == 'postgres' and matrix_appservice_irc_database_hostname == 'matrix-postgres') else [])
     +
+    ([{
+      'name': matrix_appservice_kakaotalk_database_name,
+      'username': matrix_appservice_kakaotalk_database_username,
+      'password': matrix_appservice_kakaotalk_database_password,
+    }] if (matrix_appservice_kakaotalk_enabled and matrix_appservice_kakaotalk_database_engine == 'postgres' and matrix_appservice_kakaotalk_database_hostname == 'matrix-postgres') else [])
+    +
     ([{
       'name': matrix_beeper_linkedin_database_name,
       'username': matrix_beeper_linkedin_database_username,