NOISSUE - Remove OAuth2.0 tokens from Magistrala token

[rodneyosodo]

What type of PR is this?

This is a refactor PR because it refactors how OAuth2.0 works in relation to magistrala

What does this do?

Removes OAuth2.0 tokens from magistrala token

Which issue(s) does this PR fix/relate to?

No issue

Have you included tests for your changes?

Yes, I have included tests for my changes and tested them manually.

Did you document any new/modified feature?

Yes, I have added comments to the code.

Notes

Demo https://jam.dev/c/84106a0d-f6a1-43b4-92af-23d7db977041

Explanation

From https://datatracker.ietf.org/doc/html/rfc6749#section-1.4

Access tokens are credentials used to access protected resources. An access token is a string representing an authorization issued to the client.

We only use this token once when accessing identity provider to fetch user details during registration or signup

[dborovcanin]

Make this comment a full sentence.

[dborovcanin]

Fix according to the comment. Use only a single token (access or refresh):

if ok {
		claims, ok := oauthToken.(pair)
		if !ok {
			return auth.Key{}, errors.Wrap(ErrParseToken, fmt.Errorf("invalid claims for %s token", provider.Name()))
		}

		// // access token and refresh token are not mandatory either of them can be present
		// accessToken, _ := claims[oauthAccessTokenField].(string)
		// refreshToken, _ := claims[oauthRefreshTokenField].(string)\
		switch claims.key {
		case oauthAccessTokenField:
			if err := provider.Validate(ctx, claims.value)

Also, fix the messy switch, since both cases do almost the same. Validation should inspect the error, since fallback to refresh may not make sense in some scenarios (revoked access, for example).

[dborovcanin]

Why don't we make this a map[string]string or a struct:

type pair struct {
	key   string
	value string
}

So we have:

		if key.OAuth.AccessToken != "" && key.OAuth.RefreshToken == "" {
			builder.Claim(provider.Name(), pair{
				key:   oauthAccessTokenField,
				value: key.OAuth.AccessToken,
			})
		}
		if key.OAuth.AccessToken == "" && key.OAuth.RefreshToken != "" {
			builder.Claim(provider.Name(), pair{
				key:   oauthRefreshTokenField,
				value: key.OAuth.RefreshToken,
			})
		}

[dborovcanin]

Simplify the Tokenizer Parse method. Extract validation, key parsing, and Oauth handling to three separate functions or methods.

[dborovcanin]

Use constant/enum instead of literal.