Function extract_endpoint_path_segment_variable 

pub fn extract_endpoint_path_segment_variable(segment: &str) -> Option<&str>

Available on crate feature api only.

Extract the variable of the given endpoint path segment.

The supported syntax for an endpoint path segment variable is {var}.

Returns the name of the variable if one was found in the segment, None if no variable was found.

Panics if:

• The segment begins with { but doesn’t end with }.
• The segment ends with } but doesn’t begin with {.
• The segment begins with :, which matches the old syntax for endpoint path segment variables.