Add OAuth to spec: first version

[MartenMeijboom98]

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[Copilot]

Pull Request Overview

This PR introduces OAuth 2.0 as an optional security measure in the specification, accompanied by updated documentation and diagrams that illustrate both full and DSO-only OAuth implementation scenarios.

• Added a documentation file describing OAuth 2.0 usage and its benefits as an additional security measure.
• Introduced several diagrams (sequence and component diagrams) to visually represent OAuth flows in different system configurations.

Reviewed Changes

Copilot reviewed 5 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
docs/appendix/optional-security-measures.md	Introduces OAuth 2.0 documentation and implementation recommendations.
diagrams/example-full-implementation-using-oauth-sequence.drawio	Provides a sequence diagram for a full OAuth implementation scenario.
diagrams/example-full-implementation-using-oauth-components.drawio	Provides a component diagram for full OAuth-based system interactions.
diagrams/example-dso-only-implementation-using-oauth-sequence.drawio	Provides a sequence diagram for a DSO-only OAuth implementation scenario.
diagrams/example-dso-only-implementation-using-oauth-components.drawio	Provides a component diagram for a DSO-only OAuth-based system.

Comments suppressed due to low confidence (2)

docs/appendix/optional-security-measures.md:9

• Consider rewording line 9 for clarity, for example: '...additional security measures on top of those described in the message signing mechanism.' This makes the statement clearer.

When implementing the specification, it is recommended to add additional security measures on top of the described in [message signing mechanism](message-transport-mechanism.md).

diagrams/example-full-implementation-using-oauth-components.drawio:13

• [nitpick] Consider standardizing the capitalization for provider labels; for instance, change 'DSO OAuth provider' to 'DSO OAuth Provider' to maintain consistency across diagrams.

        <mxCell id="6zocnoXHrxWYXSwQewhK-3" value="DSO OAuth provider" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1">