[TECHNICAL] Changes in transfers-related code

[JuancaG05]

There are several things to find out and some others to improve regarding transfers. Here we can list and discuss everything related with that.

THINGS TO FIND OUT:

• Is a temporal copy (in .../tmp/...) created for every type of upload? (from content URI, from system)
• Why are there 2 different types of upload in case a temporal copy is always made?
• In the case of uploads from content URI, when is the temporal copy removed?

THINGS TO IMPROVE:

• Create 2 different fields in database for transfers: sourceLocation, which can be a content URI or a path, whatever is the case, and tmpPath, which is the path where the temporal files used for uploads are located. If a temporal copy is always made, both should be always not null (at least once they get copied, which can be before the creation of the transfer object)
• TransferDao functions can use @Update or @Upsert instead of @Query
• RemoveSourceFileWorker shouldn't receive a content URI as parameter, it can be a path as well. And the key variable (KEY_PARAM_CONTENT_URI currently) should be located in the worker itself

TASKS

• Research (if needed)
• Create branch feature/feature_name
• Development tasks
  • Implement whatever
  • ...
  • Implement unit tests (if needed)
• Code review and apply changes requested
• Design test plan
• QA
• Merge branch feature/feature_name into master