Write design doc for azure-spring-security-oauth2

[chenrujun]

completed design doc: https://github.com/Azure/azure-sdk-for-java/wiki/Spring-Security-OAuth-2-for-Azure-design
Parent Epic issue: #23402

Current dependency relationship doesn't follow spring's convention.

• starter module should only contain pom. It should not contain java code / file like cosmos.enable.config / readme / changelog. For example: [azure-spring-boot-starter-keyvault-certificates] contains java code.
• starter module's com should only contain required dependencies. For example, [spring-cloud-gcp-starter-storage] only contains dependencies, but [azure-spring-cloud-starter-cache] contains build segment.
• It should be only one autoconfigure module. azure-spring-boot and azure-spring-cloud-autoconfig should combine into one module.
• It should be multiple level support when developing a starter. For example, there should be a module named azure-spring-security-oauth2-client instead of putting the logic in azure-spring-boot.
• standalone test module should not exist. Those test should move into each module. For example: [azure-spring-boot-test-keyvault] should move into azure-spring-boot-keyvault. Some integration test should convert to unit-test. (IT -> UT can skip in current issue.)

azure-spring-security-oauth2-xxx should be created.

azure-spring-security-oauth2-xxx should be created just like spring-security-oauth2-xxx.
Here is dependency relationship of spring-security-oauth2-xxx-external (spring-security-oauth2-xxx-external):

Here is dependency relationship of spring-security-oauth2-xxx-internal (spring-security-oauth2-xxx-internal)

[chenrujun]

Classes that can move into new artifact.

azure-spring-security-web

• AADHandleConditionalAccessFilter

azure-spring-security-oauth2-core

• OAuth2AuthenticatedPrincipal

azure-spring-security-oauth2-client

• AADOBOOAuth2AuthorizedClientProvider
• AADAzureDelegatedOAuth2AuthorizedClientProvider (Can move to spring-security)
• AADOAuth2AuthorizationCodeGrantRequestEntityConverter
• AADOAuth2AuthorizationRequestResolver
• AADOAuth2UserService (Can be deleted)
• AzureClientRegistration (Can move to spring-boot)

azure-spring-security-oauth2-resource-server

• JwtGrantedAuthoritiesConverter (Can move to spring-boot)
• AADJwtGrantedAuthoritiesConverter (Can move to spring-boot)
• AADJwtBearerTokenAuthenticationConverter (Can move to spring-boot)

[chenrujun]

Dependency relationship of spring-security-oauth2-xxx:

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[chenrujun]

Dependency relationship of azure-spring-security-xxx and spring-security-xxx:

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[chenrujun]

Dependency relationship of spring-boot-starter-oauth2-xxx and spring-security-xxx:

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[chenrujun]

Dependency relationship of azure-spring-boot-starter-oauth2-xxx and azure-spring-security-xxx:

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[chenrujun]

Closing this issue because design doc finished: https://github.com/Azure/azure-sdk-for-java/wiki/Spring-Security-OAuth-2-for-Azure-design