Reuse web templates in other templates (#1786)

# What this PR does

## Which issue(s) this PR fixes

## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [ ] Documentation added (or `pr:no public docs` PR label added if not
required)
- [ ] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Add helm chart support for twilio existing secrets by @atownsend247 ([#1435](https://github.com/grafana/oncall/pull/1435))
+- Add web_title, web_message and web_image_url attributes to templates ([1786](https://github.com/grafana/oncall/pull/1786))
 
 ### Changed
 

engine/apps/alerts/incident_appearance/templaters/alert_templater.py

@@ -76,7 +76,7 @@ class AlertTemplater(ABC):
         self.alert = alert
         self.slack_formatter = SlackFormatter(alert.group.channel.organization)
         self.template_manager = TemplateLoader()
-        self.incident_id = self.alert.group.inside_organization_number
+        self.alert_group_id = self.alert.group.inside_organization_number
         self.link = self.alert.group.web_link
 
     def render(self):
@@ -168,13 +168,34 @@ class AlertTemplater(ABC):
         attr_template = self.template_manager.get_attr_template(attr, channel, self._render_for())
         if attr_template is not None:
             context = {
-                "grafana_oncall_incident_id": self.incident_id,
-                "grafana_oncall_link": self.link,
                 "integration_name": channel.verbal_name,
                 "source_link": templated_alert.source_link,
-                "amixr_incident_id": self.incident_id,  # TODO: decide on variable names
-                "amixr_link": self.link,  # TODO: decide on variable names
+                "grafana_oncall_alert_group_id": self.alert_group_id,
+                "grafana_oncall_incident_id": self.alert_group_id,  # Keep for backward compatibility
+                "amixr_incident_id": self.alert_group_id,  # Keep for backward compatibility
+                "grafana_oncall_link": self.link,
+                "amixr_link": self.link,  # Keep for backward compatibility
             }
+            # Hardcoding, as AlertWebTemplater.RENDER_FOR_WEB cause circular import
+            render_for_web = "web"
+            # Propagate rendered web templates to the other templates
+            added_context = {}
+            if self._render_for() != render_for_web:
+                for attr in ["title", "message", "image_url"]:
+                    added_attr_template = self.template_manager.get_attr_template(attr, channel, render_for_web)
+                    if added_attr_template is not None:
+                        result_length_limit = (
+                            settings.JINJA_RESULT_TITLE_MAX_LENGTH
+                            if attr == "title"
+                            else settings.JINJA_RESULT_MAX_LENGTH
+                        )
+                        added_context[f"web_{attr}"] = apply_jinja_template(
+                            added_attr_template, data, result_length_limit=result_length_limit, **context
+                        )
+                    else:
+                        added_context[f"web_{attr}"] = f"web_{attr} is not set"
+                context = {**context, **added_context}
+
             try:
                 if attr == "title":
                     return apply_jinja_template(