rust: support repr(int) enum

[yjh0502]

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description

It adds support for integer-typed enums to rust client binding. Here's example schema:

openapi: 3.0.1
info:
  title: test
  version: v1
servers:
  - url: http://127.0.0.1:3000/
paths:
  /testapi:
    post:
      responses:
        '200':
          $ref: '#/components/schemas/Test'
components:
  schemas:
    Test:
      type: integer
      enum:
        - 101
        - 102

output for the schema is as follows:

 #[repr(i64)]
  #[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd, Hash, Serialize_repr, Deserialize_repr)]
  pub enum Test {
      _101 = 101,
      _102 = 102,

  }

  impl ToString for Test {
      fn to_string(&self) -> String {
          match self {
              Self::_101 => String::from("101"),
              Self::_102 => String::from("102"),
          }
      }
  }

Current implementation assumes all enums are string-represented so the schema above fails to decode int-encoded enums. This PR adds support for int-typed enums with [repr(i64)].

cc @paladinzh

[wing328]

@yjh0502 thanks for the PR.

cc @frol (2017/07) @farcaller (2017/08) @richardwhiuk (2019/07) @paladinzh (2020/05)

[wing328]

Tested locally with a spec containing an enum integer and the result is good.

running 1 test
test test_pet ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

   Doc-tests petstore-reqwest

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 01:05 min
[INFO] Finished at: 2021-07-21T16:47:04+08:00
[INFO] ------------------------------------------------------------------------

If no further feedback, I'll merge this on coming Friday.

[Hinton]

@wing328 any possibility of getting this merged? We're currently using the templates from this PR to solve it locally but it would be nice to get it included in the project. Since maintaining templates means we won't get new features automatically.