did:peer respond-in-kind behavior not working for multiuse OOB+DIDExchange

[dbluhm]

ACA-Py is intended to "respond in kind" to DID Exchange requests:

• If a did:peer:2 is sent, it should respond with a did:peer:2
• If a did:peer:4 is sent, it should respond with a did:peer:4

This works for single use invitations. However, it would seem that multi-use invitations are not behaving the same. A DID Exchange request with a did:peer:2 is being responded to with an unqualified DID but still with a did_rotate~attach, which is pretty weird...

{
  "@type": "https://didcomm.org/didexchange/1.0/response",
  "@id": "6726877c-6e06-4932-9072-123f96604e3e",
  "~thread": {
    "thid": "022cc7a4-b9b2-4fbd-9d32-05a0b9c29482",
    "pthid": "740619ba-ad06-401c-aa6d-0cf47c67624a"
  },
  "did": "4PfUhmBHLrvGfs9BRdiXB8",
  "did_rotate~attach": {
    "@id": "60785fe3-f7d6-4d9f-aac8-b933e07b71dd",
    "mime-type": "text/string",
    "data": {
      "base64": "NFBmVWhtQkhMcnZHZnM5QlJkaVhCOA==",
      "jws": {
        "header": {
          "kid": "did:key:z6Mkvj1tU2JaCN6yhSNCqrgZbbM1ujtJeUwXY9GcqzsqNwhY"
        },
        "protected": "eyJhbGciOiAiRWREU0EiLCAia2lkIjogImRpZDprZXk6ejZNa3ZqMXRVMkphQ042eWhTTkNxcmdaYmJNMXVqdEplVXdYWTlHY3F6c3FOd2hZIiwgImp3ayI6IHsia3R5IjogIk9LUCIsICJjcnYiOiAiRWQyNTUxOSIsICJ4IjogIjhjUkdxaktXcEVJSFFmOXJuMDR6NWlGQ0IyYmtENkMzazMtanhzQUN2WTgiLCAia2lkIjogImRpZDprZXk6ejZNa3ZqMXRVMkphQ042eWhTTkNxcmdaYmJNMXVqdEplVXdYWTlHY3F6c3FOd2hZIn19",
        "signature": "WYPCePSGG_Tgjcxv42MNNAxuzttGc8nZBSe6ctl3ZVphuXP-0EYzg6VptnS8VQwmJdee3Md3goHqMbxkrPlkAg"
      }
    }
  }
}