BE: Issue title and message text is not populated correctly for warning and alerts extension/update

Update templates

See https://gitlab.com/opengeoweb/geoweb-assets/-/issues/1694

About the event discussed during the meeting (one GEOMAGNETIC_STORM that later got an extension), it is correctly managed in my opinion (it cannot be viewed in the interface because it's an old event). The Json event looks like this:


```
{
 "eventid": "7e4a8e30-3bfe-11ec-91ce-cd6725cbcde8",
 "originator": "UKMO",
 "notacknowledged": true,
 "category": "GEOMAGNETIC",
 "categorydetail": "GEOMAGNETIC_STORM",
 "lifecycles": {
  "internalprovider": {
   "notifications": []
  },
  "externalprovider": {
   "owner": "UKMO",
   "eventid": "7e4a8e30-3bfe-11ec-91ce-cd6725cbcde8",
   "eventend": "2021-11-05T01:00:00Z",
   "draft": false,
   "label": "WARNING",
   "firstissuetime": "2021-11-04T08:26:11Z",
   "lastissuetime": "2021-11-04T08:26:11Z",
   "state": "issued",
   "eventstart": "2021-11-03T18:00:00Z",
   "notifications": [
    {
     "neweventend": "2021-11-05T01:00:00Z",
     "eventid": "7e4a8e30-3bfe-11ec-91ce-cd6725cbcde8",
     "changestateto": "issued",
     "label": "WARNING",
     "message": "An Earth directed CME was launched early on 2nd November following a Moderate class flare from 2891 and arrived around 03/1930 UTC. G1-G3 storming has been observed and further G3 intervals are expected with a chance of an isolated G4 interval. CME effects are likely to persist into the early hours of the 5th. This Geomagnetic Storm Watch may be superseded by Kp Alerts and Warnings where necessary as the CME arrives.",
     "neweventstart": "2021-11-03T18:00:00Z",
     "notification": {
      "potential_impacts": "An Earth directed CME was launched early on 2nd November following a Moderate class flare from 2891 and arrived around 03/1930 UTC. G1-G3 storming has been observed and further G3 intervals are expected with a chance of an isolated G4 interval. CME effects are likely to persist into the early hours of the 5th. This Geomagnetic Storm Watch may be superseded by Kp Alerts and Warnings where necessary as the CME arrives.",
      "valid_to_dt": "2021-11-05T01:00:00Z",
      "history": [
       {
        "potential_impacts": "An Earth directed CME was launched early on 2nd November following an Moderate class flare from 2891, and is modelled to arrive around 04/0000UTC. CME effects may persist into the early hours of the 5th. G1-G2 storming is considered most likely, with a chance of isolated G3 intervals, particularly on arrival and later during the passage of the magnetic cloud. This Geomagnetic Storm Watch may be superseded by Kp Alerts and Warnings where necessary as the CME arrives.",
        "initial_g_scale_estimate": null,
        "enlil_model_reference": null,
        "valid_to_dt": "2021-11-05T07:00:00Z",
        "valid_from_dt": null,
        "enlil_model_run_available": null,
        "timestamp": "2021-11-02T17:01:16"
       }
      ],
      "detail": {
       "initial_g_scale_estimate": "G3-G4",
       "enlil_model_reference": null,
       "enlil_model_run_available": false
      },
      "notification_id": "7e4a8e30-3bfe-11ec-91ce-cd6725cbcde8",
      "type": "GEOMAGNETIC_STORM_WATCH",
      "data_source": null,
      "valid_from_dt": "2021-11-03T18:00:00Z",
      "status": "SENT",
      "timestamp": "2021-11-04T08:26:11"
     },
     "categorydetail": "GEOMAGNETIC_STORM",
     "initialgscale": "G3-G4",
     "datasource": null,
     "issuetime": "2021-11-04T08:26:11Z",
     "draft": false,
     "notificationid": "7e4a8e30-3bfe-11ec-91ce-cd6725cbcde8"
    }
   ]
  }
 },
 "start_dt": "2021-11-04T08:26:11"
}
```

For reference, the two incoming events were:

```
{
 "fetchid": "61816ee8b58c954d2630126c",
 "time": 1635872491,
 "message": {
  "potential_impacts": "An Earth directed CME was launched early on 2nd November following an Moderate class flare from 2891, and is modelled to arrive around 04/0000UTC. CME effects may persist into the early hours of the 5th. G1-G2 storming is considered most likely, with a chance of isolated G3 intervals, particularly on arrival and later during the passage of the magnetic cloud. This Geomagnetic Storm Watch may be superseded by Kp Alerts and Warnings where necessary as the CME arrives.",
  "valid_to_dt": "2021-11-05T07:00:00Z",
  "history": [],
  "detail": {
   "initial_g_scale_estimate": "G1-G3",
   "enlil_model_reference": null,
   "enlil_model_run_available": false
  },
  "notification_id": "7e4a8e30-3bfe-11ec-91ce-cd6725cbcde8",
  "type": "GEOMAGNETIC_STORM_WATCH",
  "data_source": null,
  "valid_from_dt": "2021-11-03T18:00:00Z",
  "status": "SENT",
  "timestamp": "2021-11-02T17:01:16"
 },
 "type": "GEOMAGNETIC_STORM_WATCH"
}

{
 "fetchid": "618399290652348809055860",
 "time": 1636014380,
 "message": {
  "potential_impacts": "An Earth directed CME was launched early on 2nd November following a Moderate class flare from 2891 and arrived around 03/1930 UTC. G1-G3 storming has been observed and further G3 intervals are expected with a chance of an isolated G4 interval. CME effects are likely to persist into the early hours of the 5th. This Geomagnetic Storm Watch may be superseded by Kp Alerts and Warnings where necessary as the CME arrives.",
  "valid_to_dt": "2021-11-05T01:00:00Z",
  "history": [
   {
    "potential_impacts": "An Earth directed CME was launched early on 2nd November following an Moderate class flare from 2891, and is modelled to arrive around 04/0000UTC. CME effects may persist into the early hours of the 5th. G1-G2 storming is considered most likely, with a chance of isolated G3 intervals, particularly on arrival and later during the passage of the magnetic cloud. This Geomagnetic Storm Watch may be superseded by Kp Alerts and Warnings where necessary as the CME arrives.",
    "initial_g_scale_estimate": null,
    "enlil_model_reference": null,
    "valid_to_dt": "2021-11-05T07:00:00Z",
    "valid_from_dt": null,
    "enlil_model_run_available": null,
    "timestamp": "2021-11-02T17:01:16"
   }
  ],
  "detail": {
   "initial_g_scale_estimate": "G3-G4",
   "enlil_model_reference": null,
   "enlil_model_run_available": false
  },
  "notification_id": "7e4a8e30-3bfe-11ec-91ce-cd6725cbcde8",
  "type": "GEOMAGNETIC_STORM_WATCH",
  "data_source": null,
  "valid_from_dt": "2021-11-03T18:00:00Z",
  "status": "SENT",
  "timestamp": "2021-11-04T08:26:11"
 },
 "type": "GEOMAGNETIC_STORM_WATCH"
}
```

Story points: 4.0