message: fix a missing required and a description
diff: "type": "object",
  "required": [
  "@type",
  + "credentials",
  "url"
  ],
  "description": "Base class for endpoints."
  },
  "retentionPeriod": {
  "type": "string",
  - "description": "Video retention period indicates how long the video is kept in storage. Value must be specified in ISO8601 duration format (i.e. \"PT1D\" equals 1 day) and can vary between 1 day to 10 years, in 1 day increments. When absent (null), all video content is retained indefinitely. This property is only allowed for topologies where \"kind\" is set to \"live\"."
  + "description": "Video retention period indicates how long the video is kept in storage. Value must be specified in ISO8601 duration format (i.e. \"P1D\" equals 1 day) and can vary between 1 day to 10 years, in 1 day increments. When absent (null), all video content is retained indefinitely. This property is only allowed for topologies where \"kind\" is set to \"live\"."
  }
  },
  "type": "object",
  