Create new enums to type state strings and numbers on server

New enums:
- RegisteredNameFoundState (for NS lookups which emit a RegisteredNameFound signal)
    - This enum is in common/ since it is used by the common LookupResult interface
- NameRegistrationEndedState (for the NameRegistrationEnded signal)
- RegistrationState (for the RegistrationStateChanged signal)
- MessageState (for the AccountMessageStatusChanged signal)
- ConversationMemberEventType (for the ConversationMemberEvent signal)

Other changes:
- Update jamid.ts and jami-signal-interfaces.ts to use these new enums
- Update routers to use the enum members rather than magic constants

GitLab: #89
Change-Id: Ief38df0d4a35c6ecf96375bba01773e60e07b888
diff --git a/server/src/routers/nameserver-router.ts b/server/src/routers/nameserver-router.ts
index 2ead8ee..415c2d1 100644
--- a/server/src/routers/nameserver-router.ts
+++ b/server/src/routers/nameserver-router.ts
@@ -17,7 +17,7 @@
  */
 import { Router } from 'express';
 import asyncHandler from 'express-async-handler';
-import { HttpStatusCode } from 'jami-web-common';
+import { HttpStatusCode, RegisteredNameFoundState } from 'jami-web-common';
 import { Container } from 'typedi';
 
 import { Jamid } from '../jamid/jamid.js';
@@ -34,10 +34,10 @@
   asyncHandler(async (req, res) => {
     const result = await jamid.lookupUsername(req.params.username, res.locals.accountId);
     switch (result.state) {
-      case 0:
+      case RegisteredNameFoundState.Found:
         res.send(result);
         break;
-      case 1:
+      case RegisteredNameFoundState.InvalidResponse:
         res.status(HttpStatusCode.BadRequest).send('Invalid username');
         break;
       default:
@@ -52,10 +52,10 @@
   asyncHandler(async (req, res) => {
     const result = await jamid.lookupAddress(req.params.address, res.locals.accountId);
     switch (result.state) {
-      case 0:
+      case RegisteredNameFoundState.Found:
         res.send(result);
         break;
-      case 1:
+      case RegisteredNameFoundState.InvalidResponse:
         res.status(HttpStatusCode.BadRequest).send('Invalid address');
         break;
       default: