Add sliding-sync support

This allows people to try out the new Element X clients, which need to
run against the sliding-sync proxy (https://github.com/matrix-org/sliding-sync).

Supersedes https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2515

The code is based on the existing PR (#2515), but heavily reworked. Major changes:

- lots of internal refactoring and variable renaming

- fixed self-building to support non-amd64 architectures

- changed to talk to the homeserver locally, over the container network (not
  publicly)

- no more matrix-nginx-proxy support due to complexity (see below)

- no more `matrix_server_fqn_sliding_sync_proxy` in favor of
  `matrix_sliding_sync_hostname` and `matrix_sliding_sync_path_prefix`

- runs on `matrix.DOMAIN/sliding-sync` by default, so it can tried
  easily without having to create new DNS records

roles/custom/matrix-sliding-sync/templates/env.j2

@@ -0,0 +1,4 @@
+SYNCV3_SERVER={{ matrix_sliding_sync_environment_variable_syncv3_server }}
+SYNCV3_SECRET={{ matrix_sliding_sync_environment_variable_syncv3_secret }}
+SYNCV3_BINDADDR=:8008
+SYNCV3_DB={{ matrix_sliding_sync_environment_variable_syncv3_db }}

roles/custom/matrix-sliding-sync/templates/labels.j2

@@ -0,0 +1,45 @@
+{% if matrix_sliding_sync_container_labels_traefik_enabled %}
+traefik.enable=true
+
+{% if matrix_sliding_sync_container_labels_traefik_docker_network %}
+traefik.docker.network={{ matrix_sliding_sync_container_labels_traefik_docker_network }}
+{% endif %}
+
+{% set middlewares = [] %}
+
+{% if matrix_sliding_sync_container_labels_traefik_path_prefix != '/' %}
+traefik.http.middlewares.matrix-sliding-sync-slashless-redirect.redirectregex.regex=({{ matrix_sliding_sync_container_labels_traefik_path_prefix | quote }})$
+traefik.http.middlewares.matrix-sliding-sync-slashless-redirect.redirectregex.replacement=${1}/
+{% set middlewares = middlewares + ['matrix-sliding-sync-slashless-redirect'] %}
+{% endif %}
+
+{% if matrix_sliding_sync_container_labels_traefik_path_prefix != '/' %}
+traefik.http.middlewares.matrix-sliding-sync-strip-prefix.stripprefix.prefixes={{ matrix_sliding_sync_container_labels_traefik_path_prefix }}
+{% set middlewares = middlewares + ['matrix-sliding-sync-strip-prefix'] %}
+{% endif %}
+
+{% if matrix_sliding_sync_container_labels_traefik_additional_response_headers.keys() | length > 0 %}
+{% for name, value in matrix_sliding_sync_container_labels_traefik_additional_response_headers.items() %}
+traefik.http.middlewares.matrix-sliding-sync-add-headers.headers.customresponseheaders.{{ name }}={{ value }}
+{% endfor %}
+{% set middlewares = middlewares + ['matrix-sliding-sync-add-headers'] %}
+{% endif %}
+
+traefik.http.routers.matrix-sliding-sync.rule={{ matrix_sliding_sync_container_labels_traefik_rule }}
+{% if matrix_sliding_sync_container_labels_traefik_priority | int > 0 %}
+traefik.http.routers.matrix-sliding-sync.priority={{ matrix_sliding_sync_container_labels_traefik_priority }}
+{% endif %}
+traefik.http.routers.matrix-sliding-sync.service=matrix-sliding-sync
+{% if middlewares | length > 0 %}
+traefik.http.routers.matrix-sliding-sync.middlewares={{ middlewares | join(',') }}
+{% endif %}
+traefik.http.routers.matrix-sliding-sync.entrypoints={{ matrix_sliding_sync_container_labels_traefik_entrypoints }}
+traefik.http.routers.matrix-sliding-sync.tls={{ matrix_sliding_sync_container_labels_traefik_tls | to_json }}
+{% if matrix_sliding_sync_container_labels_traefik_tls %}
+traefik.http.routers.matrix-sliding-sync.tls.certResolver={{ matrix_sliding_sync_container_labels_traefik_tls_certResolver }}
+{% endif %}
+
+traefik.http.services.matrix-sliding-sync.loadbalancer.server.port=8008
+{% endif %}
+
+{{ matrix_sliding_sync_container_labels_additional_labels }}

roles/custom/matrix-sliding-sync/templates/systemd/matrix-sliding-sync.service.j2

@@ -0,0 +1,49 @@
+#jinja2: lstrip_blocks: "True"
+[Unit]
+Description=matrix-sliding-sync
+{% for service in matrix_sliding_sync_systemd_required_services_list %}
+Requires={{ service }}
+After={{ service }}
+{% endfor %}
+{% for service in matrix_sliding_sync_systemd_wanted_services_list %}
+Wants={{ service }}
+{% endfor %}
+DefaultDependencies=no
+
+[Service]
+Type=simple
+Environment="HOME={{ devture_systemd_docker_base_systemd_unit_home_path }}"
+ExecStartPre=-{{ devture_systemd_docker_base_host_command_sh }} -c '{{ devture_systemd_docker_base_host_command_docker }} kill matrix-sliding-sync 2>/dev/null || true'
+ExecStartPre=-{{ devture_systemd_docker_base_host_command_sh }} -c '{{ devture_systemd_docker_base_host_command_docker }} rm matrix-sliding-sync 2>/dev/null || true'
+
+ExecStartPre={{ devture_systemd_docker_base_host_command_docker }} create \
+			--rm \
+			--name=matrix-sliding-sync \
+			--log-driver=none \
+			--user={{ matrix_user_uid }}:{{ matrix_user_gid }} \
+			--cap-drop=ALL \
+			--read-only \
+			--tmpfs /tmp \
+			--network={{ matrix_sliding_sync_container_network }} \
+			--env-file={{ matrix_sliding_sync_base_path }}/env \
+			--label-file={{ matrix_sliding_sync_base_path }}/labels \
+			{% for arg in matrix_sliding_sync_container_extra_arguments %}
+			{{ arg }} \
+			{% endfor %}
+			{{ matrix_sliding_sync_container_image }}
+
+{% for network in matrix_sliding_sync_container_additional_networks %}
+ExecStartPre={{ devture_systemd_docker_base_host_command_docker }} network connect {{ network }} matrix-sliding-sync
+{% endfor %}
+
+ExecStart={{ devture_systemd_docker_base_host_command_docker }} start --attach matrix-sliding-sync
+
+ExecStop=-{{ devture_systemd_docker_base_host_command_sh }} -c '{{ devture_systemd_docker_base_host_command_docker }} kill matrix-sliding-sync 2>/dev/null || true'
+ExecStop=-{{ devture_systemd_docker_base_host_command_sh }} -c '{{ devture_systemd_docker_base_host_command_docker }} rm matrix-sliding-sync 2>/dev/null || true'
+
+Restart=always
+RestartSec=30
+SyslogIdentifier=matrix-sliding-sync
+
+[Install]
+WantedBy=multi-user.target