feat: Add termination functionality for rental agreements

- Introduced new entity `CKuendigung` for managing terminations.
- Added fields for termination details including date, reason, type, and status.
- Implemented backend service to initiate terminations from rental agreements.
- Created frontend handler for termination actions with confirmation dialog.
- Updated metadata and layouts for `CKuendigung` to support new functionality.
- Added internationalization support for English and German languages.
- Enhanced existing entities to establish relationships with terminations.

custom/Espo/Custom/Resources/i18n/de_DE/CMietobjekt.json

@@ -6,7 +6,8 @@
     "vmhMietverhltnises2Mietobjekt": "Mietverhältnisse (veraltet)",
     "vmhMietverhltnises": "Mietverhältnisse",
     "contactsMietobjekt": "Freigegebene Nutzer",
-    "dokumentesMietobjekt": "Dokumente"
+    "dokumentesMietobjekt": "Dokumente",
+    "kuendigungen": "Kündigungen"
   },
   "links": {
     "vmhMietverhltnises2Mietobjekt": "Mietverhältnisse (veraltet)",
@@ -14,6 +15,7 @@
     "contact2mietobjekt": "Kontakte",
     "vmhRumungsklages": "Räumungsklagen",
     "mietinkassos": "Mietinkasso",
+    "kuendigungen": "Kündigungen",
     "contactsMietobjekt": "Freigegebene Nutzer",
     "dokumentesMietobjekt": "Dokumente"
   },