Set up permissions for verify and unverify and UI for unverify

[KesterTan]

Description

Previously, any user could verify/unverify a post which would make the feature useless since a student could just verify their own post. This PR would ensure that only certain individuals are able to verify the post and that students would be unable to do so. This goes beyond just frontend logic but also protects backend API calls so that students would not be able to verify their own post by sending a CURL request.

This PR does the following:

• Adds UI for an unverified post.

• Adds permissions such that only administrators and mods can verify/unverify a post.
• Adds details about the verify message feature in the user guide in README.md

With this PR, the verify message feature can now allow only admins/mods to verify a message and the change will be propagated in both the frontend and backend (saved as a variable in the post struct). Resolves #21 and #33.

Testing

Automated unit tests for permissions have been added and lint checks are also tested.

[coveralls]

Pull Request Test Coverage Report for Build 11281935619

Details

• 8 of 8 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.007%) to 82.639%

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Totals
Change from base Build 11280055495:	0.007%
Covered Lines:	22375
Relevant Lines:	25653

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💛 - Coveralls

[katcday]

Good style and test cases look thorough! LGTM!