Add CKndigung entity and related resources

- Introduced CKndigung entity with metadata definitions including fields, links, indexes, and scopes.
- Added CKndigung controller for handling requests.
- Created internationalization files for CKndigung in multiple languages.
- Updated existing metadata and resource files to include CKndigung references.
- Enhanced global translations to support CKndigung terminology.

custom/Espo/Custom/Resources/metadata/entityDefs/Email.json

@@ -13,7 +13,8 @@
                 "CVmhVermieter",
                 "CBeteiligte",
                 "CCallQueues",
-                "CMietinkasso"
+                "CMietinkasso",
+                "CKndigung"
             ]
         }
     }