Update multipart boundary error to match Vuforia (#3044)

* Update multipart boundary error message to match Vuforia change

Vuforia dropped the "RESTEASY007550: " prefix from the error message
for missing multipart boundaries.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Update */* boundary error response to match Vuforia (400, text/plain)

Vuforia now returns 400 with text/plain;charset=utf-8 instead of
500 with application/json for the no-boundary multipart error.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: adamtheturtle

src/mock_vws/_query_validators/exceptions.py

@@ -604,18 +604,16 @@ def __init__(self) -> None:
                 raised.
         """
         super().__init__()
-        self.status_code = HTTPStatus.INTERNAL_SERVER_ERROR
-        self.response_text = (
-            "RESTEASY007550: Unable to get boundary for multipart"
-        )
+        self.status_code = HTTPStatus.BAD_REQUEST
+        self.response_text = "Unable to get boundary for multipart"
 
         date = email.utils.formatdate(
             timeval=None,
             localtime=False,
             usegmt=True,
         )
         self.headers = {
-            "Content-Type": "application/json",
+            "Content-Type": "text/plain;charset=utf-8",
             "Connection": "keep-alive",
             "Server": "nginx",
             "Date": date,

tests/mock_vws/test_query.py

@@ -179,10 +179,10 @@ class TestContentType:
             ),
             (
                 "*/*",
-                HTTPStatus.INTERNAL_SERVER_ERROR,
-                "application/json",
+                HTTPStatus.BAD_REQUEST,
+                "text/plain;charset=utf-8",
                 None,
-                "RESTEASY007550: Unable to get boundary for multipart",
+                "Unable to get boundary for multipart",
             ),
             (
                 "text/*",
@@ -404,12 +404,12 @@ def test_no_boundary(
             tell_position=requests_response.raw.tell(),
             content=requests_response.content,
         )
-        expected_text = "RESTEASY007550: Unable to get boundary for multipart"
+        expected_text = "Unable to get boundary for multipart"
         assert requests_response.text == expected_text
         assert_vwq_failure(
             response=vws_response,
-            status_code=HTTPStatus.INTERNAL_SERVER_ERROR,
-            content_type="application/json",
+            status_code=HTTPStatus.BAD_REQUEST,
+            content_type="text/plain;charset=utf-8",
             cache_control=None,
             www_authenticate=None,
             connection="keep-alive",