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/metadata/clientDefs/CVmhMietverhltnis.json

@@ -25,6 +25,16 @@
                     "iconHtml": "<span class=\"fas fa-euro-sign\"></span>",
                     "style": "warning",
                     "acl": "edit"
+                },
+                {
+                    "name": "initiateTermination",
+                    "label": "Initiate Termination",
+                    "handler": "custom:handlers/mietverhaeltnis/termination-action",
+                    "initFunction": "initInitiateTermination",
+                    "actionFunction": "actionInitiateTermination",
+                    "iconHtml": "<span class=\"fas fa-file-contract\"></span>",
+                    "style": "primary",
+                    "acl": "edit"
                 }
             ]
         }