Disable coerece_form_params option in the case of application/json

[meganemura]

To fix #286.

This disables coerece_form_params option in the case of application/json.
But, disabling coerce_form_params prevents coercing DateTime in object.

https://github.com/ota42y/openapi_parser/blob/d17334a866b39fa197d324b9d321df2b03d469b6/lib/openapi_parser/schema_validators/object_validator.rb#L41

I found that defining ObjectValidator#initialize(validator, coerce_value, datetime_coerce_class) in OpenAPIParser and adding coercing condition like below makes it working well. but I'm not sure this way is good or not.

-value.merge!(coerced_values.to_h) if @coerce_value
+value.merge!(coerced_values.to_h) if @coerce_value || !@datetime_coerce_class.nil?

[ota42y]

Thanks for the PR.
I think this PR is good, because we should not converting json by coerce_form_params=true.

When we use form/path paramemter integer will be convert string so we need string to integer.
However we don't need convet JSON because it have a types so I'd like to make this behavior the default in next major version (we shouldn't break backward compatibility).
So we need create an option called corece_json_params, and if it is not set, we should show a warning message and set 'true' (we will change default false in next version)

But, converting the datetime format string to Datetime object is useful for JSON users, so I think many user will want to use it.
So we should enable this feature separately from the corece_json_params disable.

To summarize

• Do not coerce json by coerce_form_param=true
  • This PR is goodl 👍
• Add coerce_json_param
  • We can keep the current behavior by default
  • We should change default false in next version
• Rename coerce_date_times to convert_stirng_by_datetime_formant
  • do a convert regardless of coerce_json_param=false (requires a change to openapi_parser)
  • Use coerce to convert string to OpenAPI definition types, and convert to change from OpenAPI definition types to Ruby's object.