[account] GET /accounts/:msaId response OpenApi document should define the response payload

[JoeCap08055]

Description

As a developer/user, I want to be able to understand the structure of the expected response. Currently, the GET /accounts/:msaId endpoint only defines the handle property as type object, without any details of the structure of the object.

Acceptance Criteria

• handle property is properly defined in the OpenAPI document (swagger.json) (This may entail adding details to the decorators in the code)
• All endpoints reviewed for proper definition of all payloads, and similar updates made if necessary

[JoeCap08055]

Fixed in #312