Prototype for CBA (#8475)

* Prototype for CBA

* Fixing gofmt issues

* Do not require password if logging in with certificate

* Fixing issues from feedback

* Adding unit tests

* Fixing feedback

config/default.json

@@ -337,6 +337,10 @@
         "BlockProfileRate": 0,
         "ListenAddress": ":8067"
     },
+    "ExperimentalSettings": {
+        "ClientSideCertEnable": false,
+        "ClientSideCertCheck": "secondary"
+    },
     "AnalyticsSettings": {
         "MaxUsersForStatistics": 2500
     },