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-dendrite/templates/dendrite/systemd/matrix-dendrite.service.j2

@@ -0,0 +1,65 @@
+#jinja2: lstrip_blocks: "True"
+[Unit]
+Description=Dendrite server
+{% for service in matrix_dendrite_systemd_required_services_list %}
+Requires={{ service }}
+After={{ service }}
+{% endfor %}
+{% for service in matrix_dendrite_systemd_wanted_services_list %}
+Wants={{ service }}
+{% endfor %}
+DefaultDependencies=no
+
+[Service]
+Type=simple
+Environment="HOME={{ matrix_systemd_unit_home_path }}"
+ExecStartPre=-{{ matrix_host_command_sh }} -c '{{ matrix_host_command_docker }} kill matrix-dendrite 2>/dev/null || true'
+ExecStartPre=-{{ matrix_host_command_sh }} -c '{{ matrix_host_command_docker }} rm matrix-dendrite 2>/dev/null || true'
+
+{% if 'matrix-postgres.service' in matrix_dendrite_systemd_required_services_list %}
+# Dendrite is too quick to start in relation to its matrix-postgres dependency.
+# Delay Dendrite startup to avoid failing with: "failed to connect to accounts db" ("pq: the database system is starting up").
+ExecStartPre={{ matrix_host_command_sleep }} 5
+{% endif %}
+
+ExecStart={{ matrix_host_command_docker }} run --rm --name matrix-dendrite \
+			--log-driver=none \
+			--user={{ matrix_user_uid }}:{{ matrix_user_gid }} \
+			--cap-drop=ALL \
+			--read-only \
+			--tmpfs=/tmp:rw,noexec,nosuid,size={{ matrix_dendrite_tmp_directory_size_mb }}m \
+			--network={{ matrix_docker_network }} \
+			{% if matrix_dendrite_container_http_host_bind_address and matrix_dendrite_http_bind_port %}
+			-p {{ matrix_dendrite_container_http_host_bind_address }}:{{ matrix_dendrite_http_bind_port }} \
+			{% endif %}
+			{% if matrix_dendrite_container_https_host_bind_address and matrix_dendrite_https_bind_port %}
+			-p {{ matrix_dendrite_container_https_host_bind_address }}:{{ matrix_dendrite_https_bind_port }} \
+			{% endif %}
+			--mount type=bind,src={{ matrix_dendrite_config_dir_path }},dst=/data,ro \
+			--mount type=bind,src={{ matrix_dendrite_storage_path }},dst=/matrix-media-store-parent,bind-propagation=slave \
+			--mount type=bind,src={{ matrix_dendrite_nats_storage_path }},dst=/matrix-nats-store,bind-propagation=slave \
+			{% for volume in matrix_dendrite_container_additional_volumes %}
+			-v {{ volume.src }}:{{ volume.dst }}:{{ volume.options }} \
+			{% endfor %}
+			{% for arg in matrix_dendrite_container_arguments %}
+			{{ arg }} \
+			{% endfor %}
+			{{ matrix_dendrite_docker_image }} \
+			-config /data/dendrite.yaml \
+			{{ matrix_dendrite_process_extra_arguments|join(' ') }} \
+			{% if matrix_dendrite_http_bind_address %}
+			-http-bind-address {{ matrix_dendrite_http_bind_address }}
+			{% endif %}
+			{% if matrix_dendrite_https_bind_address %}
+			-https-bind-address {{ matrix_dendrite_https_bind_address }}
+			{% endif %}
+
+ExecStop=-{{ matrix_host_command_sh }} -c '{{ matrix_host_command_docker }} kill matrix-dendrite 2>/dev/null || true'
+ExecStop=-{{ matrix_host_command_sh }} -c '{{ matrix_host_command_docker }} rm matrix-dendrite 2>/dev/null || true'
+ExecReload={{ matrix_host_command_docker }} exec matrix-dendrite /bin/sh -c 'kill -HUP 1'
+Restart=always
+RestartSec=30
+SyslogIdentifier=matrix-dendrite
+
+[Install]
+WantedBy=multi-user.target