OptionalhtmlBuild an iframe src URL for an [[html]] block.
Zero-based index matching SyntaxTree["html-blocks"]
The URL string. When empty or when the resolver is omitted,
the default pattern /{pageName}/html/{hash}-{nonce} is used.
OptionaluserLook up a user profile by username.
The raw username from [[user username]]
Profile data for rendering, or null if the user is unknown.
When null or when the resolver is omitted, the username is
rendered as plain text.
Async/sync resolver callbacks for content that depends on external data.
Unlike the parser's
DataProvider(which fetches bulk data for module expansion), these resolvers are called per-element during the rendering pass.