This declares a global `swh.ambassdor` role at realm level as it is
not attached to a particular client.
```
15:28 $ bin/octocatalog-diff --octocatalog-diff-args --no-truncate-details -t staging kelvingrove.internal.softwareheritage.org
Found host kelvingrove.internal.softwareheritage.org
Cloning into '/tmp/swh-ocd.H7JNqMuF/environments/production/data/private'...
done.
Cloning into '/tmp/swh-ocd.H7JNqMuF/environments/staging/data/private'...
done.
*** Running octocatalog-diff on host kelvingrove.internal.softwareheritage.org
I, [2021-04-27T15:28:27.188348 #375689] INFO -- : Catalogs compiled for kelvingrove.internal.softwareheritage.org
I, [2021-04-27T15:28:27.432175 #375689] INFO -- : Diffs computed for kelvingrove.internal.softwareheritage.org
diff origin/production/kelvingrove.internal.softwareheritage.org current/kelvingrove.internal.softwareheritage.org
*******************************************
Keycloak_realm[SoftwareHeritageStaging] =>
parameters =>
roles =>
+ ["swh.ambassador"]
*******************************************
Keycloak_realm[SoftwareHeritage] =>
parameters =>
roles =>
+ ["swh.ambassador"]
*******************************************
*** End octocatalog-diff on kelvingrove.internal.softwareheritage.org
```
Related to T3213