Changes to POST /api/v1/:context_id/sessions

added the non-success response with the status 503

removed the required property scope from the response with the 201 status

removed the request property scope

added the new optional request property scopes

added the required property scopes to the response with the 201 status

removed the required property scopes from the response with the 201 status

removed the request property scopes

added the new optional request property scope

added the required property scope to the response with the 201 status