Edit collaborators in repo spec

[g4s8]

Update collaborators in Repository specification on apply or create command. Now it's not clear how to edit collaborator permissions or specify it for non-organization repository. Parent #46

[orlovm]

@g4s8 GitHub does not support configurable collaborator permissions for user-owned repositories. There are only one permissions list, that collaborator can have.

Organization-owned repositories supports granular permission levels. But GitHub API looks kinda incomplete: there are five permission levels available: "read", "write", "admin", "maintain" and "triage". We can set any of this five levels, when adding a collaborator. But we can't recieve them all.1, 2 Response could contain only three permission levels, that have different names: "pull", "push", "admin". As follows "read" and "triage" will be recieved as "pull", and "write" and "maintain" as "push".

This disparity is critical for our goals, because we need spec to be identical on get and create/apply.