Make use of the existing matrix_synapse_admin_public_endpoint variable

roles/custom/matrix-synapse-admin/defaults/main.yml

@@ -43,7 +43,7 @@ matrix_synapse_admin_container_labels_traefik_enabled: true
 matrix_synapse_admin_container_labels_traefik_docker_network: "{{ matrix_synapse_admin_container_network }}"
 matrix_synapse_admin_container_labels_traefik_hostname: "{{ matrix_server_fqn_matrix }}"
 # The path prefix must either be `/` or not end with a slash (e.g. `/synapse-admin`).
-matrix_synapse_admin_container_labels_traefik_path_prefix: /synapse-admin
+matrix_synapse_admin_container_labels_traefik_path_prefix: "{{ matrix_synapse_admin_public_endpoint }}"
 matrix_synapse_admin_container_labels_traefik_rule: "Host(`{{ matrix_synapse_admin_container_labels_traefik_hostname }}`){% if matrix_synapse_admin_container_labels_traefik_path_prefix != '/' %} && PathPrefix(`{{ matrix_synapse_admin_container_labels_traefik_path_prefix | quote }}`){% endif %}"
 matrix_synapse_admin_container_labels_traefik_entrypoints: web-secure
 matrix_synapse_admin_container_labels_traefik_tls: "{{ matrix_synapse_admin_container_labels_traefik_entrypoints != 'web' }}"
@@ -130,6 +130,9 @@ matrix_synapse_admin_floc_optout_enabled: true
 # See: `matrix_synapse_admin_http_header_strict_transport_security`
 matrix_synapse_admin_hsts_preload_enabled: false
 
-# The path at which Synapse Admin will be exposed on `matrix.DOMAIN`
+# The path at which Synapse Admin will be exposed on `matrix.DOMAIN` when matrix-nginx-proxy is used.
-# (only applies when matrix-nginx-proxy is used).
+# A path of `/` is likely not a good choice when matrix-nginx-proxy is used.
+#
+# If Traefik is used, the hostname name is configurable - see `matrix_synapse_admin_container_labels_traefik_hostname`.
+# This value must either be `/` or not end with a slash (e.g. `/synapse-admin`).
 matrix_synapse_admin_public_endpoint: /synapse-admin