Inconsistent User access behaviour

[strawhat5]

Checklist:

• I've searched in the docs and FAQ for my answer
• I've included steps to reproduce the bug.

Describe the bug

We have observed many inconsistencies in the User access section, details of which are added below.

Current behavior

1. Assigning direct permission to user fails.

2. I can assign a group to a user, even though I am not the manager of that group/project. Also, on updation it always gives Created user successfully message, even though the user already exists.

3. I can unassign a group from a user, even though I am not the manager of that group/project. Gets the same Created user successfully message here.

4. Even when I am a manager, I am not able to create groups (with lower permissions) for my own project.

5. Should be able to see the permissions of all groups (View only for non-managers of that group).

6. While adding a bunch of users, it gives User already exists error (if even one of the users already exists), but successfully creates other users. Which means the Add User operation is non-atomic.

Expected behavior

All the above inconsistencies should be resolved for a smoother user experience.

[vikramdevtron]

@strawhat5 issue 1, 4, 5 unable to reproduce, found works as expected. issue 2 and 3 user message has been fixed, other will be fixed soon, created new ticket for that.
issue 6, User already exists on bulk creation has fixed in this PR.

[strawhat5]

@nishant-d Let's connect on this to see if 1, 4, 5 can be reproduced.