Multipart inputs with boundary parameter aren't parsed properly

[dmlambea]

Describe the bug
Whenever a content type like "multipart/form-data; boundary=<random string>" is processed by the decoder, the submitted data is not parsed.

Commit 41ffc11 introduced an if in line 81 which checks for an exact value of the content type "multipart/form-data". That comparison is not taking into account the optional parameter "boundary". Therefore, all parameterized submits would not succeed.

To Reproduce
Fields submitted while using the content type "multipart/form-data; boundary=thisisanexample" would fail to be parsed.

Expected behavior
The exact string "multipart/form-data" as well as "multipart/form-data; boundary=<1 to 70 chars>" must be treated the same and the data must be parsed.

Additional context
Link to Content Type header in Mozilla's MDN: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Type

[boba-keyost]

It seems that same fix needed for the case with checkJSONBodyContentType function

rest/request/jsonbody.go

Line 70 in dbcfb54

func checkJSONBodyContentType(contentType string, tolerateFormData bool) (ret bool, err error) {