[TECHNICAL] Refactor `companion` objects with same content

[jesmrec]

All the ***Operations classes inside of the package com.owncloud.android.lib.resources contain a companion object pointing to relevant endpoints, paths... as static constants.

Across the package, there are many operations that use the same strings. It could be a good idea to extract all strings to a common place. It would help in case of change, just one place to perform.

For example, the following const:

private const val GRAPH_API_DRIVES_PATH = "graph/v1beta1/drives/"

is already in 9 different operations

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