refactor: api http statuscode

[mabdh]

• Add mockery for mocking interface
• For APIs that require Auth Email header, return 403 Forbidden if not present/user does not exist
• Fix error type naming
• Create a function to check empty string
• Add tests in handler

[coveralls]

Pull Request Test Coverage Report for Build 2880992908

• 356 of 447 (79.64%) changed or added relevant lines in 22 files are covered.
• 16 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+20.03%) to 70.913%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/api/v1beta1/policy.go	9	10	90.0%
internal/api/v1beta1/project.go	43	45	95.56%
internal/store/postgres/action_repository.go	6	8	75.0%
internal/store/postgres/relation_repository.go	10	12	83.33%
internal/api/v1beta1/group.go	77	80	96.25%
internal/api/v1beta1/org.go	31	35	88.57%
internal/store/postgres/namespace_repository.go	5	9	55.56%
internal/store/postgres/role_repository.go	7	11	63.64%
internal/store/postgres/organization_repository.go	9	15	60.0%
internal/store/postgres/project_repository.go	7	13	53.85%
<!--	Total:	356	447

Files with Coverage Reduction	New Missed Lines	%
internal/api/v1beta1/permission_check.go	2	0%
internal/api/v1beta1/user.go	2	81.12%
internal/store/postgres/resource_repository.go	12	76.02%
<!--	Total:	16

Totals
Change from base Build 2866460769:	20.03%
Covered Lines:	3357
Relevant Lines:	4734

---

💛 - Coveralls

[mabdh]

Need to hold this until v0.3.x is stable enough

[mabdh]

This can be reviewed