Changes to List board sections

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

removed Paginated subschema #2 from the response body allOf list for the response status 200

added the non-success response with the status 400

added the non-success response with the status 401

added the non-success response with the status 403

added the non-success response with the status 404

added the non-success response with the status 429

added the optional property bookmark to the response with the 200 status

added the required property items to the response with the 200 status

the endpoint scheme security client_credentials was added to the API

the allOf[subschema #2] response's property type changed from no type to object for status 200

the response property allOf[subschema #2]/items/items/name became required for the status 200

added the new optional query request parameter ad_account_id

for the query request parameter page_size, the max was increased from 100.00 to 250.00

added the pattern ^\d+$ to the path request parameter board_id