ParseService will parse a proto file and return the the struct representation of that service.

Field holds information extracted by the parser about each field within each HTTP binding.

HTTPBinding holds information extracted by the parser about each HTTP binding within each method.

Method holds information extracted by the parser about each method within each service.

Service keeps track of the information extracted by the parser about each service in the file.

Service scanner conducts many of the basic scanning operatiions of a Lexer, with some additional service-specific behavior.