Do not force form-data-boundary, make it fully customizable

Author: Justin99b

src/FormDataEncoder.test.ts

@@ -59,7 +59,7 @@ test("Accepts custom boundary as the second argument", t => {
 
   const encoder = new FormDataEncoder(new FormData(), expected)
 
-  t.is(encoder.boundary, `form-data-boundary-${expected}`)
+  t.is(encoder.boundary, expected)
 })
 
 test("Has content-type string", t => {
@@ -108,7 +108,7 @@ test("Has content-type string with custom boundary string", t => {
 
   t.is(
     encoder.contentType,
-    `multipart/form-data; boundary=form-data-boundary-${expected}`
+    `multipart/form-data; boundary=${expected}`
   )
 })
 

src/FormDataEncoder.ts

@@ -175,7 +175,7 @@ export class FormDataEncoder {
     this.#CRLF_BYTES = this.#encoder.encode(this.#CRLF)
     this.#CRLF_BYTES_LENGTH = this.#CRLF_BYTES.byteLength
 
-    this.boundary = `form-data-boundary-${boundary}`
+    this.boundary = boundary;
     this.contentType = `multipart/form-data; boundary=${this.boundary}`
 
     this.#footer = this.#encoder.encode(