WFE2: Add unit tests for draft-12/draft-13 intercompat. (#3816)

The implementation of the `features.ACME13KeyRollover` flag was written
with the intent to allow client developers to send both the `"newKey"`
and `"oldKey"` and be interoperable between both feature flag states. We
should have an explicit unit test for this to be sure it works as
intended.

wfe2/wfe_test.go

@@ -2127,6 +2127,22 @@ func TestKeyRollover(t *testing.T) {
 		   }`,
 			NewKey: newKeyPriv,
 		},
+		{
+			Name:    "Valid key rollover request, added ACME13KeyRollover compat",
+			Payload: `{"newKey":` + string(newJWKJSON) + `, "oldKey":` + test1KeyPublicJSON + `, "account":"http://localhost/acme/acct/1"}`,
+			ExpectedResponse: `{
+		     "id": 1,
+		     "key": ` + string(newJWKJSON) + `,
+		     "contact": [
+		       "mailto:person@mail.com"
+		     ],
+		     "agreement": "http://example.invalid/terms",
+		     "initialIp": "",
+		     "createdAt": "0001-01-01T00:00:00Z",
+		     "status": "valid"
+		   }`,
+			NewKey: newKeyPriv,
+		},
 		{
 			Name:              "ACME13KeyRollover, legacy rollover request",
 			ACME13KeyRollover: true,
@@ -2191,6 +2207,23 @@ func TestKeyRollover(t *testing.T) {
 		   }`,
 			NewKey: newKeyPriv,
 		},
+		{
+			Name:              "ACME13KeyRollover, Valid key rollover request, legacy compat",
+			ACME13KeyRollover: true,
+			Payload:           `{"oldKey":` + test1KeyPublicJSON + `, "newKey":` + string(newJWKJSON) + `, "account":"http://localhost/acme/acct/1"}`,
+			ExpectedResponse: `{
+		     "id": 1,
+		     "key": ` + string(newJWKJSON) + `,
+		     "contact": [
+		       "mailto:person@mail.com"
+		     ],
+		     "agreement": "http://example.invalid/terms",
+		     "initialIp": "",
+		     "createdAt": "0001-01-01T00:00:00Z",
+		     "status": "valid"
+		   }`,
+			NewKey: newKeyPriv,
+		},
 	}
 
 	for _, tc := range testCases {