Changes to get session

added the non-success response with the status 503

the response's body type changed from object to no type for status 200

removed the optional property apiKeyId from the response with the 200 status

removed the optional property clientLabel from the response with the 200 status

removed the optional property clientMetadata from the response with the 200 status

removed the optional property createdAt from the response with the 200 status

removed the optional property endTime from the response with the 200 status

removed the optional property engineHost from the response with the 200 status

removed the optional property engineProtocol from the response with the 200 status

removed the optional property engineVersion from the response with the 200 status

removed the optional property exitStatus from the response with the 200 status

removed the optional property id from the response with the 200 status

removed the optional property organizationId from the response with the 200 status

removed the optional property personaConfig from the response with the 200 status

removed the optional property personaId from the response with the 200 status

removed the optional property sessionLengthMs from the response with the 200 status

removed the optional property startTime from the response with the 200 status

removed the optional property updatedAt from the response with the 200 status

added Session subschema #2 to the response body allOf list for the response status 200

added the non-success response with the status 403