This aligns the last writing endpoints to use BaseModel (Origin, OriginVisit) objects as input and OriginVisit as output.
After adding the type effectivelyype (for before it's the type after deducing how it's used, here is the comparison:it was not defined yet) :
```
before def origin_visit_add(self, origin: Dict,str, date: Union[str, datetime.datetime], type: str) -> Optional[Dict[str, Union[str, int]]]:
after def origin_visit_add(self, origin: Origin_url: str, date: Union[str, datetime.datetime], type: str) -> OriginVisit:
```
Impacts:
- swh-loader-core (runtime)
- swh-loader-svn (runtime)
- swh-journal (tests)
- swh-web (tests)
- swh-indexer (tests)
Depends on D2813