This adapts the main service template to actually reference the sentry setup.
As it's common for all journal clients, no point in making that setup more complex (as the first implem of this diff did):
```
$ $SWH_PUPPET_ENVIRONMENT_HOME/bin/octocatalog-diff --octocatalog-diff-args --no-truncate-details --to staging search0
...
*******************************************
File[/etc/systemd/system/swh-search-journal-client@.service] =>
parameters =>
content =>
@@ -8,4 +8,7 @@
_
[Service]
+Environment=SWH_SENTRY_DSN=https://swh::deploy::search::sentry_token@sentry.softwareheritage.org/15
+Environment=SWH_SENTRY_ENVIRONMENT=staging
+Environment=SWH_MAIN_PACKAGE=swh.search
User=swhstorage
Group=swhstorage
*******************************************
Systemd::Unit_file[swh-search-journal-client@.service] =>
parameters =>
content =>
@@ -8,4 +8,7 @@
_
[Service]
+Environment=SWH_SENTRY_DSN=https://swh::deploy::search::sentry_token@sentry.softwareheritage.org/15
+Environment=SWH_SENTRY_ENVIRONMENT=staging
+Environment=SWH_MAIN_PACKAGE=swh.search
User=swhstorage
Group=swhstorage
*******************************************
*** End octocatalog-diff on search0.internal.staging.swh.network
```