Remove backup / restore endpoint

In the past, the backup / restore endpoint has been implemented in
ConfAPI to be able to perform export / import operations via REST API,
which was long a missing feature in Confluence. The endpoint was fully
working, but never really fully finished.

In the last years, Atlassian has finally implemented an own official
backup / restore endpoint. In order to achieve this, they also fully
reimplemented the whole related internal Java API, and deprecated the
whole related old Java API.

Porting the existing backend / restore endpoint onto the new Java API
would be equal to a full reimplementation. For this reason, the endpoint
that has always been 'experimental' is removed again in favor of the
official endpoint.

README.md

@@ -16,3 +16,5 @@ Resources
 ---------
 
 The documentation can be found [HERE](index.adoc).
+
+For a detailed list of breaking changes in specific versions, please refer to our [Version History](VERSIONS.md).

VERSIONS.md

@@ -0,0 +1,14 @@
+Version history
+===============
+
+## 0.1.0
+
+With the release of Confluence 8.2.0, Atlassian has introduced an official backup and restore endpoint, enabling the export and import of spaces and entire sites via REST API.
+This functionality aligns with what was previously provided by ConfAPI for Confluence.
+In developing this new endpoint, Atlassian has completely redeveloped the internal Java codebase for handling space exports and imports, which was the foundation for ConfAPI's backup functionality.
+
+Given these changes, maintaining ConfAPI's backup endpoint to provide identical functionality to Atlassian's official solution would require a complete redevelopment of our endpoint.
+Consequently, we have decided to discontinue the ConfAPI backup endpoint.
+Users seeking backup and restore capabilities are encouraged to transition to Atlassian's official endpoint:
+
+* [Official Atlassian Confluence Backup and Restore REST API Endpoint](https://docs.atlassian.com/ConfluenceServer/rest/8.2.0/#api/backup-restore)