feat(synapse): support Postgres database keepalive options

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

@@ -1329,6 +1329,9 @@ matrix_synapse_database_host: ''
 matrix_synapse_database_port: 5432
 matrix_synapse_database_cp_min: 5
 matrix_synapse_database_cp_max: 10
+matrix_synapse_database_keepalives_idle: null
+matrix_synapse_database_keepalives_interval: null
+matrix_synapse_database_keepalives_count: null
 matrix_synapse_database_user: "synapse"
 matrix_synapse_database_password: ""
 matrix_synapse_database_database: "synapse"

roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2

@@ -868,6 +868,15 @@ database:
     port: {{ matrix_synapse_database_port }}
     cp_min: {{ matrix_synapse_database_cp_min | to_json }}
     cp_max: {{ matrix_synapse_database_cp_max | to_json }}
+{% if matrix_synapse_database_keepalives_idle is not none %}
+    keepalives_idle: {{ matrix_synapse_database_keepalives_idle | to_json }}
+{% endif %}
+{% if matrix_synapse_database_keepalives_interval is not none %}
+    keepalives_interval: {{ matrix_synapse_database_keepalives_interval | to_json }}
+{% endif %}
+{% if matrix_synapse_database_keepalives_count is not none %}
+    keepalives_count: {{ matrix_synapse_database_keepalives_count | to_json }}
+{% endif %}
 
 
 ## Logging ##