feat(errors): Add API and docs for new "request blocked" errno 125.

docs/api.md

@@ -84,6 +84,7 @@ The currently-defined error responses are:
 * status code 400, errno 122:  account is not locked
 * status code 400, errno 123:  unknown device
 * status code 400, errno 124:  session already registered by another device
+* status code 400, errno 125:  request blocked for security reasons
 * status code 400, errno 126:  account must be reset
 * status code 503, errno 201:  service temporarily unavailable to due high load (see [backoff protocol](#backoff-protocol))
 * status code 503, errno 202:  feature has been disabled for operational reasons

lib/error.js

@@ -28,6 +28,7 @@ var ERRNO = {
   MISSING_CONTENT_LENGTH_HEADER: 112,
   MISSING_PARAMETER: 108,
   REQUEST_TOO_LARGE: 113,
+  REQUEST_BLOCKED: 125,
   SERVER_BUSY: 201,
   SERVER_CONFIG_ERROR: 100,
   THROTTLED: 114,
@@ -346,6 +347,15 @@ AppError.tooManyRequests = function (retryAfter) {
   )
 }
 
+AppError.requestBlocked = function () {
+  return new AppError({
+    code: 400,
+    error: 'Request blocked',
+    errno: ERRNO.REQUEST_BLOCKED,
+    message: 'The request was blocked for security reasons'
+  })
+}
+
 AppError.serviceUnavailable = function (retryAfter) {
   if (!retryAfter) {
     retryAfter = 30