Function include 

pub fn include(_item: TokenStream) -> TokenStream

The idea for this macro

• Collect the config, that contains
  • this module path
  • original prost-generated structs module path
  • maybe structs and enums postfix
  • a prost-generated file that has a name of proto package (or specify)
  • a number of structs specs
    • struct fqn
    • array of required fields
    • array of additional attributes
  • a number of enums
    • enum fqn
    • array of additional attributes
• For each linked file
  • Read and load the file into token streams
  • Traverse the AST, collecting
    • for each struct
      • struct fqn, AST, array of fields with field type
      • enum fqn, AST, array of variants with variant inner type if any
• Traverse the collected data
  • validate that all configured structs and enums do exist
  • either
    • related types (option, hashmap, vec) are also configured
    • related types (option, hashmap, vec) are also added to the config
  • if conditions are not met, throw an error
    • unknown struct
    • unknwon field
    • related type is not configured
• Assemble the module AST, including
  • error type
  • conversion functions (option, hashmap, vec) (TryFrom, Into)