R echo client tests (#17629)

* add r echo api client sample

* add r workflow

* fix

* add env

* set r version

* install curl

* install dep

* fix

* comment out installation

samples/client/echo_api/r/docs/FormApi.md

@@ -0,0 +1,118 @@
+# FormApi
+
+All URIs are relative to *http://localhost:3000*
+
+Method | HTTP request | Description
+------------- | ------------- | -------------
+[**TestFormIntegerBooleanString**](FormApi.md#TestFormIntegerBooleanString) | **POST** /form/integer/boolean/string | Test form parameter(s)
+[**TestFormOneof**](FormApi.md#TestFormOneof) | **POST** /form/oneof | Test form parameter(s) for oneOf schema
+
+
+# **TestFormIntegerBooleanString**
+> character TestFormIntegerBooleanString(integer_form = var.integer_form, boolean_form = var.boolean_form, string_form = var.string_form)
+
+Test form parameter(s)
+
+Test form parameter(s)
+
+### Example
+```R
+library(openapi)
+
+# Test form parameter(s)
+#
+# prepare function argument(s)
+var_integer_form <- 56 # integer |  (Optional)
+var_boolean_form <- "boolean_form_example" # character |  (Optional)
+var_string_form <- "string_form_example" # character |  (Optional)
+
+api_instance <- FormApi$new()
+# to save the result into a file, simply add the optional `data_file` parameter, e.g.
+# result <- api_instance$TestFormIntegerBooleanString(integer_form = var_integer_form, boolean_form = var_boolean_form, string_form = var_string_formdata_file = "result.txt")
+result <- api_instance$TestFormIntegerBooleanString(integer_form = var_integer_form, boolean_form = var_boolean_form, string_form = var_string_form)
+dput(result)
+```
+
+### Parameters
+
+Name | Type | Description  | Notes
+------------- | ------------- | ------------- | -------------
+ **integer_form** | **integer**|  | [optional] 
+ **boolean_form** | **character**|  | [optional] 
+ **string_form** | **character**|  | [optional] 
+
+### Return type
+
+**character**
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+ - **Content-Type**: application/x-www-form-urlencoded
+ - **Accept**: text/plain
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | Successful operation |  -  |
+
+# **TestFormOneof**
+> character TestFormOneof(form1 = var.form1, form2 = var.form2, form3 = var.form3, form4 = var.form4, id = var.id, name = var.name)
+
+Test form parameter(s) for oneOf schema
+
+Test form parameter(s) for oneOf schema
+
+### Example
+```R
+library(openapi)
+
+# Test form parameter(s) for oneOf schema
+#
+# prepare function argument(s)
+var_form1 <- "form1_example" # character |  (Optional)
+var_form2 <- 56 # integer |  (Optional)
+var_form3 <- "form3_example" # character |  (Optional)
+var_form4 <- "form4_example" # character |  (Optional)
+var_id <- 56 # integer |  (Optional)
+var_name <- "name_example" # character |  (Optional)
+
+api_instance <- FormApi$new()
+# to save the result into a file, simply add the optional `data_file` parameter, e.g.
+# result <- api_instance$TestFormOneof(form1 = var_form1, form2 = var_form2, form3 = var_form3, form4 = var_form4, id = var_id, name = var_namedata_file = "result.txt")
+result <- api_instance$TestFormOneof(form1 = var_form1, form2 = var_form2, form3 = var_form3, form4 = var_form4, id = var_id, name = var_name)
+dput(result)
+```
+
+### Parameters
+
+Name | Type | Description  | Notes
+------------- | ------------- | ------------- | -------------
+ **form1** | **character**|  | [optional] 
+ **form2** | **integer**|  | [optional] 
+ **form3** | **character**|  | [optional] 
+ **form4** | **character**|  | [optional] 
+ **id** | **integer**|  | [optional] 
+ **name** | **character**|  | [optional] 
+
+### Return type
+
+**character**
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+ - **Content-Type**: application/x-www-form-urlencoded
+ - **Accept**: text/plain
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | Successful operation |  -  |
+