Changes to Create broadcast

removed the enum value instagram of the request property channel

removed the enum value messenger of the request property channel

removed the enum value voice of the request property channel

removed the instagram enum value from the broadcast/channel response property for the response status 201

removed the instagram enum value from the broadcast/channel response property for the response status 409

removed the messenger enum value from the broadcast/channel response property for the response status 201

removed the messenger enum value from the broadcast/channel response property for the response status 409

removed the voice enum value from the broadcast/channel response property for the response status 201

removed the voice enum value from the broadcast/channel response property for the response status 409

added the new messenger enum value to the broadcast/channel response property for the response status 201

added the new messenger enum value to the broadcast/channel response property for the response status 409

added the new messenger enum value to the request property channel

added the new optional request property content/templateHeaderVariables

added the optional property broadcast/content/templateHeaderVariables to the response with the 201 status

added the optional property broadcast/content/templateHeaderVariables to the response with the 409 status

added the new optional request property content/templateButtonVariables

added the optional property broadcast/content/templateButtonVariables to the response with the 201 status

added the optional property broadcast/content/templateButtonVariables to the response with the 409 status