enable operator support for pg15 and drop support for 9.5 and 9.6 (#2140)

* enable operator support for pg15 and drop support for 9.5 and 9.6
* not offer 15 in UI before spilo-15 is available

ui/operator_ui/main.py

@@ -321,7 +321,7 @@ DEFAULT_UI_CONFIG = {
     'users_visible': True,
     'databases_visible': True,
     'resources_visible': RESOURCES_VISIBLE,
-    'postgresql_versions': ['11','12','13','14'],
+    'postgresql_versions': ['11', '12', '13', '14'],
     'dns_format_string': '{0}.{1}',
     'pgui_link': '',
     'static_network_whitelist': {},

ui/operator_ui/spiloutils.py

@@ -308,7 +308,7 @@ def read_versions(
         if uid == 'wal' or defaulting(lambda: UUID(uid))
     ]
 
-BACKUP_VERSION_PREFIXES = ['', '9.5/', '9.6/', '10/', '11/', '12/', '13/', '14/']
+BACKUP_VERSION_PREFIXES = ['', '9.6/', '10/', '11/', '12/', '13/', '14/', '15/']
 
 def read_basebackups(
     pg_cluster,