Document cds watch --with-mtx (#2145)

Author: swaldmann

guides/multitenancy/index.md

@@ -292,12 +292,6 @@ This is a known issue in CDS 9.
 
 ## Test-Drive Locally {#test-locally}
 
-For local testing, create a new profile that contains the multitenancy configuration:
-
-```sh
-cds add multitenancy --for local-multitenancy
-```
-
 <div class="impl java">
 
   For multitenancy you need additional dependencies in the _pom.xml_ of the `srv` directory. To support mock users in the local test scenario add `cds-starter-cloudfoundry`:
@@ -316,7 +310,7 @@ cds add multitenancy --for local-multitenancy
   ```yaml [application.yaml]
   ---
   spring:
-    config.activate.on-profile: local-multitenancy
+    config.activate.on-profile: with-mtx
   #...
   cds:
     multi-tenancy:
@@ -335,25 +329,6 @@ cds add multitenancy --for local-multitenancy
 
   :::
 
-Configure the sidecar to use dummy authentication.
-
-::: code-group
-
-```json [mtx/sidecar/package.json]
-{
-  "cds": {
-    "profile": "mtx-sidecar",
-    "[development]": {
-      "requires": {
-        "auth": "dummy"
-      }
-    }
-  }
-}
-```
-
-:::
-
 </div>
 
 Before deploying to the cloud, you can test-drive common SaaS operations with your app locally, including SaaS startup, subscribing tenants, and upgrading tenants.
@@ -410,7 +385,7 @@ In the following steps, we start two servers, the main app and MTX sidecar, and
 <div class="impl node">
 
    ```sh
-   cds watch --profile local-multitenancy
+   cds watch --with-mtx
    ```
 
    ::: details  Persistent database
@@ -446,15 +421,15 @@ In the following steps, we start two servers, the main app and MTX sidecar, and
 
   ```sh
   cd srv
-  mvn cds:watch -Dspring-boot.run.profiles=local-multitenancy
+  mvn cds:watch -Dspring-boot.run.profiles=with-mtx
   ```
 
   ::: details  Persistent database
 
   The server starts as usual, with the difference that a persistent database is used automatically instead of an in-memory one:
 
   ```log
-  2023-03-31 14:19:23.987  INFO 68528 --- [  restartedMain] c.s.c.bookshop.Application               : The following 1 profile is active: "local-mtxs"
+  2023-03-31 14:19:23.987  INFO 68528 --- [  restartedMain] c.s.c.bookshop.Application               : The following 1 profile is active: "with-mtx"
   ...
   2023-03-31 14:19:23.987  INFO 68528 --- [  restartedMain] c.s.c.services.impl.ServiceCatalogImpl   : Registered service ExtensibilityService$Default
   2023-03-31 14:19:23.999  INFO 68528 --- [  restartedMain] c.s.c.services.impl.ServiceCatalogImpl   : Registered service CatalogService