[InviteController] Clean up logic and add tests

[imnasnainaec]

Progress on #2647

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This change is 

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
Backend/Controllers/InviteController.cs	91.86% <93.75%> (+91.86%)	⬆️

... and 206 files with indirect coverage changes

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[jasonleenaylor]

Reviewed 4 of 4 files at r2, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @imnasnainaec and @jmgrady)

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Backend/Controllers/InviteController.cs line 150 at r2 (raw file):

        public bool IsTokenValid { get; set; }
        [Required]
        public bool isUserValid { get; set; }

Is (C# style for properties)

Code quote:

is

[imnasnainaec]

Reviewable status: 2 of 4 files reviewed, 1 unresolved discussion (waiting on @jasonleenaylor and @jmgrady)

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Backend/Controllers/InviteController.cs line 150 at r2 (raw file):

Previously, jasonleenaylor (Jason Naylor) wrote…

Is (C# style for properties)

Done.

[jasonleenaylor]

Reviewed 2 of 2 files at r3, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @jmgrady)