Proc mac support map param (#544)

* feat(proc_macro): add support for map arguments

* feat(proc_macro): formatting

* feat(proc_macro): fix issues with Into trait

* feat(proc_macro): param_format for methods

* feat(proc_macro): improve param_format checking

- Addressed @niklasad1

's suggestion to use an Option instead of just
defaulting to "array".

* feat(proc_macro): apply suggestions, add test case

- Use enum for param format.
- Extract parsing logic into separate function.
- Add ui test.

* feat(proc_macro): run cargo fmt

* feat(proc_macro): address suggestions

* feat(proc_macro): document param_kind argument

* feat(proc_macro):  consistent spacing

Apply @maciejhirsz formatting suggestion.

Co-authored-by: Maciej Hirsz <[email protected]>

* feat(proc_macro): apply suggestions

- make parameter encoding DRY
- remove strings from param_kind
- return result from parse_param_kind

* feat(proc_macro): formatting

Co-authored-by: Maciej Hirsz <[email protected]>