url package:openapi3

The authorization URL to be used for OAuth2 flow. This SHOULD be in the form of a URL.
The token URL to be used for OAuth2 flow. This SHOULD be in the form of a URL.
The URL pointing to the contact information.
The URL for the target documentation.
A URL to the license used for the API.
The URL to be used for obtaining refresh tokens.
A URL to the target host. This URL supports Server Variables and MAY be relative, to indicate that the host location is relative to the location where the OpenAPI document is being served. Variable substitutions will be made when a variable is named in {brackets}.