Url.Interpolate provides a primary entrypoint function, interpolate, which takes
a URI Template string and a variable, and expands
the input string according to the rules in IETF RFC 6570,
up to Level 4.
the Context for a template interpolation
Works like Dict.fromList to produce a context of names to Scalar string values; you could also use this to create an empty context like
simpleContext []add a scalar (in other words a simple string) value to the context
add a list of strings to the context
add an associated list (in other words a map) to a context
Example URI template interpolation: