# Summary

Introduces versioning for entities.

# Focus

Important classes/changes:

* `src/main/java/caosdb/server/entity/Version.java` - the class that represents an entity version. The XML Serialization is done by `src/main/java/caosdb/server/entity/xml/VersionXMLSerializer.java`. Parsing is not necessary as for now.
* `src/main/java/caosdb/server/resource/AbstractCaosDBServerResource.java` - In this class the requested entities are parsed from the last URI path segment. Until now, we assumed, that everything which is not an integer is a name. Therefore we had two  separate getters for requested ids and requested names. Since this assumption is not true anymore, we only have one. This results in changes in several other classes (grep for that method).
* Maybe not so easy to understand: `retrieveValidSparseEntityById` in `src/main/java/caosdb/server/jobs/Job.java`. This is a convenient method to get the entity from the container (if present) or from the database. See the code comments and please come back to me, if that is not sufficient.

If not-to-be-changed entities are in container.

f-select-subproperties -> dev

# Summary

See summary of https://gitlab.com/caosdb/caosdb-webui/-/merge_requests/72

Funny side note: this MR !47 and the issue it resolves #47 have the same number  

# Focus

* The important changes are in `RetrieveFullEntity.java`, `EntityToElementStrategy.java` and `SetFieldStrategy.java`.
  * `RetrieveFullEntity.java` is responsible for the retrieval of entities and it needed additional functionality to retrieve referenced entities recursively. It does this but only if a list of `Query.Selects` is there and non-empty, because this is the case when the request is a SELECT query.
  * `EntityToElementStrategy.java` is responsible for the xml generation. It was kind of buggy and I did some refactoring there.
  * `SetFieldStrategy.java` is decides whether a property of an entity is to be included in the generated output (xml) or not. 
Additional functionality is added to cope with deeply nested references.
* Note: I also deleted the AWI stuff, because I didn't want to refactor these classes.

# Test Environment

See https://gitlab.com/caosdb/caosdb-webui/-/merge_requests/72

# Check List for the Author

- [x] All automated tests pass
- [x] Reference related Issues
- [x] Up-to-date CHANGELOG.md
- [x] Annotations in code (Gitlab comments)
  - Intent of new code
  - Problems with old code
  - Why this implementation?


# Check List for the Reviewer


- [x] I understand the intent of this MR
- [x] All automated tests pass
- [x] Up-to-date CHANGELOG.md
- [ ] The test environment setup works and the intended behavior is
  reproducible in the test environment
- [x] In-code documentation and comments are up-to-date.
- [ ] Check: Are there spezifications? Are they satisfied?

For further good practices have a look at [our review guidelines](https://gitlab.com/caosdb/caosdb/-/blob/dev/REVIEW_GUIDELINES.md).

See merge request caosdb/caosdb-server!47

For issue #97.

f-one-time-tokens -> dev

See merge request caosdb/caosdb-server!40

EHN: special handling of html files in shared resource.

See merge request caosdb/caosdb-server!48

The shared resource returns files of all media types as download
attachments except for HTML files, which should be opened by the browser
directly.

Also a bit of documentation.