Camunda Run Spring Security OAuth2 integration

User Story (Required on creation)

As an administrator, I want to be able to use a camunda-provided docker image with minimal customization, dropping some code and jars to the userLib folder to enable SSO integration.

Functional Requirements (Required before implementation)

See product-hub epic.

Technical Requirements (Required before implementation)

Integrate Spring Security into Spring Boot & Camunda Run.
Provide out of the box oauth2 integrations with Camunda auth flows for the Webapps.

Limitations of Scope

We do not provide OIDC specific support.

Hints

Breakdown

### Tasks
- [ ] https://github.com/camunda/camunda-bpm-platform/issues/4451
- [ ] https://github.com/camunda/camunda-bpm-platform/issues/4452
- [ ] https://github.com/camunda/camunda-bpm-platform/issues/4453
- [ ] https://github.com/camunda/camunda-bpm-platform/issues/4454
- [ ] https://github.com/camunda/camunda-bpm-platform/issues/4455
- [ ] Add login plugin with SSO option

Dev2QA handover

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camunda / camunda-bpm-platform

Camunda Run Spring Security OAuth2 integration #4450