What is this feature?
Allows the creation of alert rules with mimirtool in a specified folder.
Why do we need this feature?
Currently, the APIs for mimirtool create namespaces and rule groups in the root folder without the ability to set a custom folder. For example, it could be a special "Imported" folder, etc.
This PR makes it possible with a special header: mimirtool ... --extra-headers="X-Grafana-Alerting-Folder-UID=123". If it's not present, the root folder is used, otherwise, the specified one is used.
mimirtool does not support nested folder structures, while Grafana allows folder nesting. To keep compatibility, we return only direct child folders of the working folder (as namespaces) with rule groups and rules that are directly in these child folders as if there are no nested folders.
For example, given this folder structure in Grafana:
```
grafana/
├── production/
│ ├── service1/
│ │ └── alerts/
│ └── service2/
└── testing/
└── service3/
```
If the working folder is "grafana":
Only namespaces "production" and "testing" are returned
Only rule groups directly within these folders are included
If the working folder is "production":
- Only namespaces "service1" and "service2" are returned
Only rule groups directly within these folders are included
Initially, Metadata had only the EditorSettings, and HasMetadata was used to understand if the incoming update request had metadata in the body because it could be omitted if it was empty. For example, when the rule is updated via the provisioning API or has only false values. If it was in the request, we used that; if not, we used the metadata from the existing rule from the database. If the rule was updated via the AlertRuleService, we didn't change Metadata at all if the rule already existed.
But now, Metadata also has the Prometheus rule definition, and we always need to update it with the new version of the AlertRuleService when the rule exists in the DB and has the same UID. HasMetadata is renamed to HasEditorSettings to keep the old behaviour only for EditorSettings.
Now, the provisioning API and the conversion API will overwrite everything except EditorSettings with the new data.
What is this feature?
Adds an API endpoint to create alert rules with mimirtool:
- POST /convert/prometheus/config/v1/rules/{NamespaceTitle} - Accepts a single rule group in a Prometheus YAML format and creates or updates a Grafana rule group from it.
The endpoint uses the conversion package from #100224.
Key parts
The API works similarly to the provisioning API. If the rule does not exist, it will be created, otherwise updated. Any rules not present in the new group will be deleted, ensuring the group is fully synchronized with the provided configuration.
Since the API works with namespace titles (folders), the handler automatically creates a folder in the root based on the provided title if it does not exist. It also requires a special header, X-Grafana-Alerting-Datasource-UID. This header specifies which datasource to use for the new rules.
If the rule group's evaluation interval is not specified, it uses the DefaultRuleEvaluationInterval from settings.
