fix: check for resource.ErrNotExist error in check permission

[rsbh]

Problem.
If a random ID is passed in the CheckFederatedResourcePermission API resource body. The API throws an Internal error. And in the server logs, the error is resource doesn't exist.
After debugging, I found that we fetch the resource from the db, and it returns ErrNotExist error.
This error was not handled in the API handler function.

This PR adds a check for the resource.ErrNotExist error. It also refactors the switch statement.

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
frontier	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Oct 28, 2024 10:01am

[coveralls]

Pull Request Test Coverage Report for Build 11551576193

Details

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.003%) to 30.829%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/api/v1beta1/permission_check.go	0	1	0.0%

Files with Coverage Reduction	New Missed Lines	%
internal/api/v1beta1/permission_check.go	1	34.13%

Totals
Change from base Build 11516797820:	0.003%
Covered Lines:	7623
Relevant Lines:	24727

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💛 - Coveralls

[anujk14]

lgtm