[Schema Inaccuracy] installation-token.expires_at is string. Should be date-time

[rahulsom]

Schema Inaccuracy

This is the schema

      "installation-token": {
        "title": "Installation Token",
        "description": "Authentication token for a GitHub App installed on a user or org.",
        "type": "object",
        "properties": {
          ...
          "expires_at": {
            "type": "string"
          },
        }
      } 

This is in the example

        {
          "token": "ghs_16C7e42F292c6912E7710c838347Ae178B4a",
          "expires_at": "2016-07-11T22:14:10Z",
          "permissions": {
            "issues": "write",
            "contents": "read"
          }
          ...
        }

Expected

That field could be a date-time

Reproduction Steps

I see this in

• fpt
• ghec
• ghes-3.14
• ghes-3.15
• ghes-3.16
• ghes-3.17
• ghes-3.18
• ghes-3.19