Define instanceId property on workers

This give us the possibility to run multiple instances of
workers that that don't expose a port.

Right now, we don't support that, but in the future we could
run multiple `federation_sender` or `pusher` workers, without
them fighting over naming (previously, they'd all be named
something like `matrix-synapse-worker-pusher-0`, because
they'd all define `port` as `0`).

roles/matrix-synapse/tasks/synapse/workers/util/inject_systemd_services_for_worker.yml

@@ -1,6 +1,18 @@
+# The tasks below run before `validate_config.yml`.
+# To avoid failing with a cryptic error message, we'll do validation here.
+#
+# This check is mostly relevant to people who explicitly define `matrix_synapse_workers_enabled_list`
+# (Synapse Workers users from the earlier days of this PR - https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/456).
+#
+# In the future, it should be possible to remove this check.
+# Our own code which dynamically builds `matrix_synapse_workers_enabled_list` does things right.
+- name: Fail if instanceId not defined for worker
+  fail:
+    msg: "Synapse workers (like {{ matrix_synapse_worker_details|to_json }}) need to define an instanceId property (type + instanceId must be unique)"
+  when: "'instanceId' not in matrix_synapse_worker_details"
 
 - set_fact:
-    matrix_synapse_worker_systemd_service_name: "matrix-synapse-worker-{{ matrix_synapse_worker_details.type }}-{{ matrix_synapse_worker_details.port }}.service"
+    matrix_synapse_worker_systemd_service_name: "matrix-synapse-worker-{{ matrix_synapse_worker_details.type }}-{{ matrix_synapse_worker_details.instanceId }}.service"
 
 - set_fact:
     matrix_systemd_services_list: "{{ matrix_systemd_services_list + [matrix_synapse_worker_systemd_service_name] }}"

roles/matrix-synapse/tasks/synapse/workers/util/setup_files_for_worker.yml

@@ -1,12 +1,11 @@
-
 - set_fact:
-    matrix_synapse_worker_systemd_service_name: "matrix-synapse-worker-{{ matrix_synapse_worker_details.type }}-{{ matrix_synapse_worker_details.port }}"
+    matrix_synapse_worker_systemd_service_name: "matrix-synapse-worker-{{ matrix_synapse_worker_details.type }}-{{ matrix_synapse_worker_details.instanceId }}"
 
 - set_fact:
     matrix_synapse_worker_container_name: "{{ matrix_synapse_worker_systemd_service_name }}"
 
 - set_fact:
-    matrix_synapse_worker_config_file_name: "worker.{{ matrix_synapse_worker_details.type }}_{{ matrix_synapse_worker_details.port }}.yaml"
+    matrix_synapse_worker_config_file_name: "worker.{{ matrix_synapse_worker_details.type }}_{{ matrix_synapse_worker_details.instanceId }}.yaml"
 
 - name: Ensure configuration exists for {{ matrix_synapse_worker_systemd_service_name }}
   template: