fix(auth/middleware): only enforce email matches on OIDC method tokens

[GeorgeMac]

Fixes an issue where when OIDC is used in conjunction with other authentication methods (Token, Kubernetes etc.) with the new email matches feature, we end up inadvertantly rejecting all non-OIDC method generated tokens.

The email matches feature should only be enforced on authentication tokens generated with the OIDC method.

From the newly added test around this behaviour:

    --- FAIL: TestEmailMatchingInterceptor/successful_token_was_not_generated_via_OIDC_method (0.00s)
        logger.go:130: 2023-08-01T14:41:44.690Z	DEBUG	no email provided but required for auth
        middleware_test.go:281: 
            	Error Trace:	/src/internal/server/auth/middleware_test.go:281
            	Error:      	Not equal: 
            	            	expected: <nil>(<nil>)
            	            	actual  : *status.Error(&status.Error{s:(*status.Status)(0xc0000143d8)})
            	Test:       	TestEmailMatchingInterceptor/successful_token_was_not_generated_via_OIDC_method

This is a authentication token created as a static token failing because of email matches which only should apply to client token generated with the OIDC method.

[codecov]

Codecov Report

Merging #1934 (de57a17) into main (9c08bc5) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1934      +/-   ##
==========================================
+ Coverage   71.35%   71.36%   +0.01%     
==========================================
  Files          66       66              
  Lines        6455     6458       +3     
==========================================
+ Hits         4606     4609       +3     
  Misses       1592     1592              
  Partials      257      257              

Files Changed	Coverage Δ
internal/server/auth/middleware.go	90.17% <100.00%> (+0.27%)	⬆️

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