feature: allowEmptyValue controls (#4788)

* add baseline tests

* coerce empty strings to null when updating parameter values

* add ParameterIncludeEmpty

* add redux management for empty parameter value inclusion state

* use name+in keying for state management instead of hash keying

* update new redux method usages to name+in keying

* coerce empty Immutable iterables in onChangeWrapper

* OAS3 tests & support

* add included empty parameters to requests before dispatching to Swagger Client

* make empty inclusion interface prettier

* add tests for #4587

* linter fixes

* check for truthy value before reaching into property

src/core/components/parameter-include-empty.jsx

@@ -0,0 +1,27 @@
+import React from "react"
+import cx from "classnames"
+import PropTypes from "prop-types"
+import ImPropTypes from "react-immutable-proptypes"
+
+export const ParameterIncludeEmpty = ({ param, isIncluded, onChange, isDisabled }) => {
+  const onCheckboxChange = e => {
+    onChange(e.target.checked)
+  }
+  if(!param.get("allowEmptyValue")) {
+    return null
+  }
+  return <div className={cx("parameter__empty_value_toggle", {
+    "disabled": isDisabled
+  })}>
+    <input type="checkbox" disabled={isDisabled} checked={!isDisabled && isIncluded} onChange={onCheckboxChange} />
+    Send empty value
+  </div>
+}
+ParameterIncludeEmpty.propTypes = {
+  param: ImPropTypes.map.isRequired,
+  isIncluded: PropTypes.bool.isRequired,
+  isDisabled: PropTypes.bool.isRequired,
+  onChange: PropTypes.func.isRequired,
+}
+
+export default ParameterIncludeEmpty