Document learning about extra fields

Author: adamtheturtle

CONTRIBUTING.rst

@@ -168,7 +168,7 @@ However, other `Vuforia Web Services documentation <https://library.vuforia.com/
 The documentation page `How To Perform an Image Recognition Query <https://library.vuforia.com/articles/Solution/How-To-Perform-an-Image-Recognition-Query>`__ states that the ``Content-Type`` header must be set to ``multipart/form-data``.
 However, it must be set to ``multipart/form-data; boundary=<BOUNDARY>`` where ``<BOUNDARY>`` is the boundary used when encoding the form data.
 
-The documentation page `How To Perform an Image Recognition Query <https://library.vuforia.com/articles/Solution/How-To-Perform-an-Image-Recognition-Query>`__ states that ``Content-Type`` with be the only response header.
+The documentation page `How To Perform an Image Recognition Query <https://library.vuforia.com/articles/Solution/How-To-Perform-an-Image-Recognition-Query>`__ states that ``Content-Type`` will be the only response header.
 This is not the case.
 
 The documentation page `How To Perform an Image Recognition Query <https://library.vuforia.com/articles/Solution/How-To-Perform-an-Image-Recognition-Query>`__ states that 10 is the maximum allowed value of ``max_num_results``.
@@ -180,6 +180,9 @@ After deleting a target, for up to approximately 30 seconds, matching it with a
 
 A target with the name ``\uffff`` gets stuck in processing.
 
+The documentation page `How To Perform an Image Recognition Query <https://library.vuforia.com/articles/Solution/How-To-Perform-an-Image-Recognition-Query>`__ states that "The API accepts requests with unknown data fields, and ignore the unknown fields.".
+This is not the case.
+
 Performing a release
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