List provider types the gateway can construct, with their credential forms

A valid request URL is required to generate request examples

[
  {
    "default_base_url": "<string>",
    "fields": [
      {
        "advanced": true,
        "name": "<string>",
        "options": [
          "<string>"
        ],
        "required": true
      }
    ],
    "type": "<string>"
  }
]

{
  "code": "<string>",
  "message": "<string>",
  "param": "<string>",
  "provider": "<string>",
  "status_code": 123,
  "type": "provider_error"
}

{
  "code": "<string>",
  "message": "<string>",
  "param": "<string>",
  "provider": "<string>",
  "status_code": 123,
  "type": "provider_error"
}