Query: Fix rendered JSON state value for rules and alerts should be in lowercase

[s-urbaniak]

Currently, alert state is rendered as upper case.
In Prometheus it is lower case.
This fixes it.

Signed-off-by: Sergiusz Urbaniak sergiusz.urbaniak@gmail.com

Fixes #2830

• I added CHANGELOG entry for this change.
• Change is not relevant to the end user.

Changes

• the web /apiv1/rules endpoint renders alert states now in lowercase to retain compatibility with the Prometheus API.

Verification

• Changed unit tests
• Verified manually in a local setup:

$ curl -s localhost:32775/api/v1/rules | jq .
{
  "status": "success",
  "data": {
    "groups": [
      {
        "name": "example_abort",
        "file": "/shared/rules/rules-0.yaml",
        "rules": [
          {
            "state": "inactive",
            "name": "TestAlert_AbortOnPartialResponse",
            "query": "absent(some_metric)",
            "duration": 0,
            "labels": {
              "replica": "rule1",
              "severity": "page"
            },
            "annotations": {
              "summary": "I always complain, but I don't allow partial response in query."
            },
            "alerts": [],
            "health": "err",
            "lastError": "no query API server reachable",
            "evaluationTime": 0.00042013,
            "lastEvaluation": "2020-07-02T11:36:10.20089108Z",
            "type": "alerting"
          }
        ],
        "interval": 3,
        "evaluationTime": 0,
        "lastEvaluation": "0001-01-01T00:00:00Z",
        "partial_response_strategy": "WARN",
        "partialResponseStrategy": "ABORT"
      },
      {
        "name": "example_warn",
        "file": "/shared/rules/rules-1.yaml",
        "rules": [
          {
            "state": "inactive",
            "name": "TestAlert_WarnOnPartialResponse",
            "query": "absent(some_metric)",
            "duration": 0,
            "labels": {
              "replica": "rule1",
              "severity": "page"
            },
            "annotations": {
              "summary": "I always complain and allow partial response in query."
            },
            "alerts": [],
            "health": "err",
            "lastError": "no query API server reachable",
            "evaluationTime": 0.000391637,
            "lastEvaluation": "2020-07-02T11:36:11.856795352Z",
            "type": "alerting"
          }
        ],
        "interval": 3,
        "evaluationTime": 0,
        "lastEvaluation": "0001-01-01T00:00:00Z",
        "partial_response_strategy": "WARN",
        "partialResponseStrategy": "WARN"
      }
    ]
  }
}

[brancz]

There appear to be a couple more occurrences in tests that need to be fixed. Otherwise lgtm

[s-urbaniak]

@brancz all green, PTAL :-)

[brancz]

Thank you!