Add role based authorization

[JigarJoshi]

Support role based access control in Tigris.

For the initial phase

• Support three roles [owner, editor, readonly].
• The user who creates the namespace becomes owner.
• The user can invite other users by assigning the roles with invitation.
• Allow/disallow operations based on their roles.

Also support finer grain permission modeling to extend it in next phase.

[rodneyosodo]

Hi there! I am interested in contributing to this project and would like to request permission to work on this issue. I have experience with the technologies involved and believe I can provide a useful contribution to the project. Please let me know if there are any specific guidelines or instructions I should follow when working on this issue. Thank you!