System Console: Email notification content setting (#7122)

* PLT-7195: Added new config option, new license feature, and config UI to system console. Still need to implement behaviour change in email batching code

* PLT-7195: Modified batch emails to respect email notification content type setting

* PLT-7195: Tweaking the colours a bit

* PLT-7195: Added support for email notification content type setting in immediate (non-batched) notification messages. Attempted to clean up the code somewhat. Unit tests coming in a future commit

* PLT-7195: Added unit tests for non-batched emails

* Checked license when applying email content settings

* Changed return type of getFormattedPostTime

config/config.json

@@ -143,7 +143,8 @@
         "EnableEmailBatching": false,
         "EmailBatchingBufferSize": 256,
         "EmailBatchingInterval": 30,
-        "SkipServerCertificateVerification": false
+        "SkipServerCertificateVerification": false,
+        "EmailNotificationContentsType": "full"
     },
     "RateLimitSettings": {
         "Enable": false,