feature: support for Parameter.content (#5571)

* add `getParameterSchema` OAS helper

* use `Parameter.content.[firstKey].schema` as schema value when present

* `newValue` -> `initialValue`

* make `paramWithMeta` a const

* add trailing comma to `swagger2SchemaKeys`

* refactor `helpers` to a folder

* deprecate `src/core/utils.js` in favor of `src/core/helpers/`

* support `Parameter.content.[mediaType].schema` in validateParam

* reject `null` as an OAS3 object value

* expose Fetch errors in the browser console

* generate ParameterRow default values based on `content` values

* add tests for `getParameterSchema`

* remove debugger statement

* remove debugger statement

* don't apply `generatedSampleValue`s to parameters with `examples`

* remove extra semi

* disable JSON check in parameter runtime validation

* stringify JsonSchema_object textarea values

* add Cypress tests

* swagger-client@3.9.4

src/core/json-schema-components.jsx

@@ -4,6 +4,7 @@ import { List, fromJS } from "immutable"
 import cx from "classnames"
 import ImPropTypes from "react-immutable-proptypes"
 import DebounceInput from "react-debounce-input"
+import { stringify } from "core/utils"
 //import "less/json-schema-form"
 
 const noop = ()=> {}
@@ -269,7 +270,7 @@ export class JsonSchema_object extends PureComponent {
         <TextArea
           className={cx({ invalid: errors.size })}
           title={ errors.size ? errors.join(", ") : ""}
-          value={value}
+          value={stringify(value)}
           disabled={disabled}
           onChange={ this.handleOnChange }/>
       </div>