Add "credential management" page to the docs to describe how to work with CSRF tokens, API tokens, and API access credentials

Tasks:

• Create a page which describes the two types of credentials in Sonador
• Describe the role of CSRF tokens and the purpose of the CSRF token endpoint
• Describe the structure of the APIs: endpoints, operations, and data payloads. Include sample requests. Refer to oak-tree/medical-imaging/sonador!54.
• Describe how API credential and token management is implemented in the Sonador IO Client. Include example code. Refer to oak-tree/medical-imaging/sonador-client!38 for functional test cases which can be used for reference.