feat: allow plain text as request body

Author: mnorlin

src/openapi-typescript/fetch-factory.ts

@@ -64,7 +64,10 @@ function buildInit(
 ): RequestInit {
   return {
     ...Object.assign({}, { ...defaultInit }, { ...options }),
-    body: options.body ? JSON.stringify(options.body) : undefined,
+    body:
+      options.body && typeof options.body == "object"
+        ? JSON.stringify(options.body)
+        : options.body,
     method: options.method?.toUpperCase(),
     headers,
   };

src/openapi-typescript/types/fetch-options.ts

@@ -23,7 +23,7 @@ export type FetchOptions<Operation> = Omit<
  */
 export type AllFetchOptions<Operation = never> = Omit<RequestInit, "body"> & {
   parameters: FetchParameters<Operation>;
-  body: OperationRequestBody<Operation>;
+  body: OperationRequestBody<Operation> | string;
 };
 
 /**