Fix UTF-8 not allowed in Equal field for inhibition rules

[grobinson-grafana]

This commit fixes a bug where UTF-8 characters are not allowed in the Equal field for inhibition rules, even when UTF-8 strict mode is enabled.

This bug occurred because we forgot to override the validation in model.LabelName. I have copied the same logic used for GroupBy with GroupByStr, adding EqualStr.

We would like to upgrade prometheus/common in future and use the validation there instead, but it presents challenges with downstream projects like Mimir and Cortex where, at present, UTF-8 can be enabled and disabled in separate components at the same time, which is not supported in prometheus/common.

[grobinson-grafana]

I did a full test of this, including the inhibiting behavior, and can confirm that it works. The first test was without an emoji in equal as a control test:

inhibit_rules:
    - equal:
        - baz
      source_matchers:
        - "foo\U0001F642=bar"
      target_matchers:
        - "bar\U0001F642=baz"

and we can see that the alert was inhibited:

[
  {
    "annotations": {},
    "endsAt": "2024-12-21T02:23:33.061Z",
    "fingerprint": "3381011f87e9020c",
    "receivers": [
      {
        "name": "default"
      }
    ],
    "startsAt": "2024-12-21T02:18:33.061Z",
    "status": {
      "inhibitedBy": [
        "c72bcc07a25e8ca7"
      ],
      "mutedBy": null,
      "silencedBy": [],
      "state": "suppressed"
    },
    "updatedAt": "2024-12-21T02:18:33.061Z",
    "labels": {
      "bar🙂": "baz",
      "baz": "corge"
    }
  },
  {
    "annotations": {},
    "endsAt": "2024-12-21T02:23:27.690Z",
    "fingerprint": "c72bcc07a25e8ca7",
    "receivers": [
      {
        "name": "default"
      }
    ],
    "startsAt": "2024-12-21T02:18:27.690Z",
    "status": {
      "inhibitedBy": [],
      "mutedBy": null,
      "silencedBy": [],
      "state": "active"
    },
    "updatedAt": "2024-12-21T02:18:27.690Z",
    "labels": {
      "baz": "corge",
      "foo🙂": "bar"
    }
  }
]

The second test used the same matchers, but equal contains an emoji:

inhibit_rules:
    - equal:
        - "baz\U0001F642"
      source_matchers:
        - "foo\U0001F642=bar"
      target_matchers:
        - "bar\U0001F642=baz"

[
  {
    "annotations": {},
    "endsAt": "2024-12-21T02:25:27.553Z",
    "fingerprint": "50e470c7e420595a",
    "receivers": [
      {
        "name": "default"
      }
    ],
    "startsAt": "2024-12-21T02:20:27.553Z",
    "status": {
      "inhibitedBy": [
        "81366be48b8b7751"
      ],
      "mutedBy": null,
      "silencedBy": [],
      "state": "suppressed"
    },
    "updatedAt": "2024-12-21T02:20:27.553Z",
    "labels": {
      "bar🙂": "baz",
      "baz🙂": "corge"
    }
  },
  {
    "annotations": {},
    "endsAt": "2024-12-21T02:25:21.385Z",
    "fingerprint": "81366be48b8b7751",
    "receivers": [
      {
        "name": "default"
      }
    ],
    "startsAt": "2024-12-21T02:20:21.385Z",
    "status": {
      "inhibitedBy": [],
      "mutedBy": null,
      "silencedBy": [],
      "state": "active"
    },
    "updatedAt": "2024-12-21T02:20:21.385Z",
    "labels": {
      "baz🙂": "corge",
      "foo🙂": "bar"
    }
  }
]

[grobinson-grafana]

I also tested with two alerts that matched the target matchers, however, with the expectation that just one of those alerts is inhibited as it has a matching equal label. The first test was without an emoji as a control test:

inhibit_rules:
    - equal:
        - baz
      source_matchers:
        - "foo\U0001F642=bar"
      target_matchers:
        - "bar\U0001F642=baz"

[
  {
    "annotations": {},
    "endsAt": "2024-12-21T02:32:55.511Z",
    "fingerprint": "3381011f87e9020c",
    "receivers": [
      {
        "name": "default"
      }
    ],
    "startsAt": "2024-12-21T02:27:55.511Z",
    "status": {
      "inhibitedBy": [
        "c72bcc07a25e8ca7"
      ],
      "mutedBy": null,
      "silencedBy": [],
      "state": "suppressed"
    },
    "updatedAt": "2024-12-21T02:27:55.511Z",
    "labels": {
      "bar🙂": "baz",
      "baz": "corge"
    }
  },
  {
    "annotations": {},
    "endsAt": "2024-12-21T02:33:00.138Z",
    "fingerprint": "ae726b055d42000d",
    "receivers": [
      {
        "name": "default"
      }
    ],
    "startsAt": "2024-12-21T02:28:00.138Z",
    "status": {
      "inhibitedBy": [],
      "mutedBy": null,
      "silencedBy": [],
      "state": "active"
    },
    "updatedAt": "2024-12-21T02:28:00.138Z",
    "labels": {
      "bar🙂": "baz",
      "baz": "jorge"
    }
  },
  {
    "annotations": {},
    "endsAt": "2024-12-21T02:32:50.699Z",
    "fingerprint": "c72bcc07a25e8ca7",
    "receivers": [
      {
        "name": "default"
      }
    ],
    "startsAt": "2024-12-21T02:27:50.699Z",
    "status": {
      "inhibitedBy": [],
      "mutedBy": null,
      "silencedBy": [],
      "state": "active"
    },
    "updatedAt": "2024-12-21T02:27:50.699Z",
    "labels": {
      "baz": "corge",
      "foo🙂": "bar"
    }
  }
]

The second test uses the same matchers, but the equal label has an emoji:

inhibit_rules:
    - equal:
        - "baz\U0001F642"
      source_matchers:
        - "foo\U0001F642=bar"
      target_matchers:
        - "bar\U0001F642=baz"

[
  {
    "annotations": {},
    "endsAt": "2024-12-21T02:35:58.223Z",
    "fingerprint": "50e470c7e420595a",
    "receivers": [
      {
        "name": "default"
      }
    ],
    "startsAt": "2024-12-21T02:30:58.223Z",
    "status": {
      "inhibitedBy": [
        "81366be48b8b7751"
      ],
      "mutedBy": null,
      "silencedBy": [],
      "state": "suppressed"
    },
    "updatedAt": "2024-12-21T02:30:58.223Z",
    "labels": {
      "bar🙂": "baz",
      "baz🙂": "corge"
    }
  },
  {
    "annotations": {},
    "endsAt": "2024-12-21T02:36:01.436Z",
    "fingerprint": "5e88f11e42a70d0b",
    "receivers": [
      {
        "name": "default"
      }
    ],
    "startsAt": "2024-12-21T02:31:01.436Z",
    "status": {
      "inhibitedBy": [],
      "mutedBy": null,
      "silencedBy": [],
      "state": "active"
    },
    "updatedAt": "2024-12-21T02:31:01.436Z",
    "labels": {
      "bar🙂": "baz",
      "baz🙂": "jorge"
    }
  },
  {
    "annotations": {},
    "endsAt": "2024-12-21T02:35:54.303Z",
    "fingerprint": "81366be48b8b7751",
    "receivers": [
      {
        "name": "default"
      }
    ],
    "startsAt": "2024-12-21T02:30:54.303Z",
    "status": {
      "inhibitedBy": [],
      "mutedBy": null,
      "silencedBy": [],
      "state": "active"
    },
    "updatedAt": "2024-12-21T02:30:54.303Z",
    "labels": {
      "baz🙂": "corge",
      "foo🙂": "bar"
    }
  }
]