test(Common): add tests for Types/Metrics/RecordingRuleDefinitionUtil

[suvvvv]

What

Adds unit tests for the RecordingRuleDefinitionUtil class in Common/Types/Metrics/RecordingRuleDefinition.ts, which previously had no test coverage.

Covered:

• getAggregationOptions — every option has a label and a valid AggregationType value.
• getNextAlias — A when empty, the first unused letter otherwise, and skips gaps (e.g. A, C → B).
• getEmptyDefinition — a single A source with expression A, and that it validates once a metric name is set.
• getValidationError — the full set of branches: missing definition, no sources, too many sources, invalid alias, duplicate alias, missing metric name, half-specified attribute filter, missing/over-length expression, undefined alias reference, alias-less expression, and characters outside the DSL grammar. Plus the happy path returning null.

Why

Improves test coverage for the Common/Types utilities (part of the broader test-coverage effort).

Testing

node node_modules/.bin/jest --runInBand ./Tests/Types/Metrics/RecordingRuleDefinition.test.ts

All 19 tests pass. The file is Prettier-clean.

[simlarsen]

✅ Snyk checks have passed. No issues have been found so far.

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