feat(op): authorize callback handler as argument in legacy server registration

[muhlemmer]

This change requires an additional argument to the op.RegisterLegacyServer constructor which passes the Authorize Callback Handler. This allows implementations to use their own handler instead of the one provided by the package. The current handler is exported for legacy behavior.

This change is not considered breaking, as RegisterLegacyServer is flagged experimental.

Related to https://github.com/zitadel/zitadel/issues/6882

Definition of Ready

• [x] I am happy with the code
• [x] Short description of the feature/issue is added in the pr description
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• [x] Acceptance criteria are met
• [x] All open todos and follow ups are defined in a new ticket and justified
• [x] Deviations from the acceptance criteria and design are agreed with the PO and documented.
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• [x] Critical parts are tested automatically
• [x] Where possible E2E tests are implemented
• [x] Documentation/examples are up-to-date
• [x] All non-functional requirements are met
• [x] Functionality of the acceptance criteria is checked manually on the dev system.

[github-actions[bot]]

:tada: This PR is included in version 3.23.0 :tada:

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