Alerting: Allow sending notification tags to Opsgenie as extra properties (#30332)

* Alerting: Opsgenie send tags as extra properties

Allow users to select where to send notification tags when alerting via
OpsGenie. Supports sending tags as key/value details, concatenated
strings in tags or both.

Users will be able to see their tags as key/values under extra
properties in an alert on the Opsgenie UI. These key/values can
then be used in the platform for routing, templating etc.

  * Configurable delivery to either tags, extra properties or both

  * Default to current behaviour (tags only)

  * Support both so users can transition from tags to details

Add docs and clean up references

* Alerting: Add additional arg for Opsgenie tests

The NewEvalContext function now requires a 'PluginRequestValidator' argument.
As our test does not use the validator we can specify 'nil' to satisfy the
function and allow our test to pass as expected.

* Alerting: Opsgenie doc fixes

Accept suggested changes for Opsgenie docs

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

* Alerting: Opsgenie provisioning settings docs

Add the new setting to the provisioning docs

* Alerting: Opsgenie doc typo correction

Move the comma (,) out of the preformatting tags for the setting value

* Alerting: Opsgenie refactor send switches

Refactor the send switches to be methods on the OpsgenieNotiefier
itself. This also cleans up the method names so that the code reads
a bit more logically as:

if we should send details: send details
if we should send tags: send tags

This avoids the calling code needing to care about passing the state
and allows an engineer working in the `createAlert` function to focus
on the results of applying the logic instead.

* Alerting: Opsgenie docs rename note


Rename the note heading to match the number to more clearly link them.

* Alerting: Opsgenie use standard reference to note

Refer to the note below as per recommendation and standards.

Fixes #30331

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

docs/sources/administration/provisioning.md

@@ -541,6 +541,7 @@ The following sections detail the supported settings and secure settings for eac
 | apiUrl           |                |
 | autoClose        |                |
 | overridePriority |                |
+| sendTagsAs       |                |
 
 #### Alert notification `telegram`
 

docs/sources/alerting/notifications.md

@@ -59,7 +59,7 @@ Hipchat | `hipchat` | yes, external only | no
 [Kafka](#kafka) | `kafka` | yes, external only | no
 Line | `line` | yes, external only | no
 Microsoft Teams | `teams` | yes, external only | no
-OpsGenie | `opsgenie` | yes, external only | yes
+[Opsgenie](#opsgenie) | `opsgenie` | yes, external only | yes
 [Pagerduty](#pagerduty) | `pagerduty` | yes, external only | yes
 Prometheus Alertmanager | `prometheus-alertmanager` | yes, external only | yes
 [Pushover](#pushover) | `pushover` | yes | no
@@ -111,6 +111,19 @@ Token | If provided, Grafana will upload the generated image via Slack's file.up
 
 If you are using the token for a slack bot, then you have to invite the bot to the channel you want to send notifications and add the channel to the recipient field.
 
+### Opsgenie
+
+To setup Opsgenie you will need an API Key and the Alert API Url. These can be obtained by configuring a new [Grafana Integration](https://docs.opsgenie.com/docs/grafana-integration).
+
+Setting | Description
+--------|------------
+Alert API URL | The API URL for your Opsgenie instance. This will normally be either `https://api.opsgenie.com` or, for EU customers, `https://api.eu.opsgenie.com`.
+API Key | The API Key as provided by Opsgenie for your configured Grafana integration.
+Override priority | Configures the alert priority using the `og_priority` tag. The `og_priority` tag must have one of the following values: `P1`, `P2`, `P3`, `P4`, or `P5`. Default is `False`.
+Send notification tags as | Specify how you would like [Notification Tags]({{< relref "create-alerts.md/#notifications" >}}) delivered to Opsgenie. They can be delivered as `Tags`, `Extra Properties` or both. Default is Tags. See note below for more information.
+
+> **Note:** When notification tags are sent as `Tags` they are concatenated into a string with a `key:value` format. If you prefer to receive the notifications tags as key/values under Extra Properties in Opsgenie then change the `Send notification tags as` to either `Extra Properties` or `Tags & Extra Properties`.
+
 ### PagerDuty
 
 To set up PagerDuty, all you have to do is to provide an integration key.