fix: change oauth type in asyncapi schema

[spataphore1337]

Description

Added changes to the generation of AsyncAPI documentation in the OAuthBearer part. According to the AsyncAPI specification, the OAuthBearer is mapped to oauth2. Also adds a “$ref” field for mapping and generating documentation. It should be clarified in the future whether requiring this field is a bug or whether additional edits are needed.

Thank you to the following developers for their help:

1. @Lancetnik for help with the bug and support during the fix;
2. @KrySeyt for consultations on AsyncAPI in FastStream;
3. @three-question-marks for spending time together while fixing this problem and studying AsyncAPI documentation at the same time;
4. @dalelane for help in mapping Kafka Security Config to AsyncAPI types

Fixes #1631

Type of change

Please delete options that are not relevant.

• Documentation (typos, code examples, or any documentation updates)
• Bug fix (a non-breaking change that resolves an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a fix or feature that would disrupt existing functionality)
• This change requires a documentation update

Checklist

• My code adheres to the style guidelines of this project (scripts/lint.sh shows no errors)
• I have conducted a self-review of my own code
• I have made the necessary changes to the documentation
• My changes do not generate any new warnings
• I have added tests to validate the effectiveness of my fix or the functionality of my new feature
• Both new and existing unit tests pass successfully on my local environment by running scripts/test-cov.sh
• I have ensured that static analysis tests are passing by running scripts/static-analysis.sh
• I have included code examples to illustrate the modifications