Sandbox response for limited results does not match spec

[mikemonteith]

Describe the bug
Sandbox returns 400 instead of 200 for TOO_MANY_MATCHES response

To Reproduce
Use the postman definition for "Search with limited results" to make a search request that returns too many results
The HTTP response code is 400, and issue[0].code is "not-found"

Expected behavior
Should return a 200 message with issue[0].code === "multiple-matches"

Screenshots