Remove blank space on rewrited operationId

[VitorVRS]

The operationId is usually used in the URL (e.g: Swagger UI), so URLs should contain only safe chars.

The inspiration for this PR is the spectral linter validation: https://github.com/stoplightio/spectral/blob/develop/packages/rulesets/src/oas/index.ts#L296

[mbuhot]

IMO this should raise an error rather than re-writing the operation ID.
There's a chance that the "#{operation_id}_#{occurrence}" convention will conflict with an operation ID the library user has explicitly put on one of their operations.

[zorbash]

There are some additional issues with make_operation_ids_unique/1.
For update actions defined using the resource macro, like:

resources "/pets", OpenApiSpexTest.PetController, only: [:update]

both patch and put are handled by the same function which leads to duplicate operation ids. If there's nothing the user can do to prevent this, then raising an error might cause frustration.

Another issue with make_operation_ids_unique/1 is that it doesn't respect operation_id: nil.

operationId is an optional unique string used to identify an operation. If provided, these IDs must be unique
among all operations described in your API.

operationId is optional, but if one tries to skip it, the duplicate operation for the put verb will have a " (2)" operation_id, which will certainly be unexpected.

  1) test Paths from_router (OpenApiSpex.PathsTest)
     test/paths_test.exs:7
     Assertion with in failed
     code:  assert "OpenApiSpexTest.PetController.update" in operation_ids
     left:  "OpenApiSpexTest.PetController.update"
     right: [nil, " (2)"]
     stacktrace:
       test/paths_test.exs:20: (test)

My suggestion is to make it an open_api_spex configuration. Keep "#{operation_id} (#{occurrence})" as the default for backwards compatibility and add the following options:

• raise - raises an error
• verb_suffix - Suffixes the operation ID of each duplicate with the verb, "#{operation_id}_#{verb}". This makes generated operation_id more deterministic since it does not depend on the order that paths are loaded.

In any case, when the operation_id is nil, it should be preserved.