Read Datadog monitors stored as objects

[ryanduffin]

cortex_catalog_entity no longer crashes when an entity's Datadog monitors are stored as objects.

Claude Details

Summary

• The Cortex API accepts a Datadog monitor as a bare ID (- 123) or as an object with an ID and an optional alias (- id: 123). The object form came with Datadog multi-account support.
• The parser read only the bare form. An unchecked type assertion (monitor.(int)) panicked on the object form, so plan, apply, and refresh crashed for any entity with object-form monitors.

Changes

• interpolateDataDogApm reads both forms through a new dataDogMonitorID helper. interpolateApm and interpolateDataDogApm now return an error, as interpolateSLOs already does.
• IDs are parsed as integers (int, int64, or a base-10 string inside an object), not through float64. Fractions, infinity, and values outside the int64 range are errors.
• The rules follow the backend parser:
  • A bare string monitor is an error. The API converts a string ID only inside an object and drops a bare string.
  • Every non-null alias is an error, including "", which the API treats as an alias name. The schema has no alias attribute, so reading only the ID would drop the alias on the next apply, and the monitor would move to the default Datadog configuration without a message. The error tells the user to remove the alias in Cortex.
• A Datadog APM value that is not an object, or monitors that is not a list, is an error, not a panic.
• GetFromDescriptor adds the entity tag to parse errors, so the user can see which entity failed.
• CHANGELOG entry.

Not in this PR

• Alias support in the schema. This needs a new attribute, because a change to the type of monitors would break current configurations.
• Other unchecked casts in the parser (for example the New Relic applicationId, the SLO maps, and the top-level section casts in YamlToEntity) can still panic on unexpected input.

Test plan

• go test ./...: all packages pass.
  • TestYamlToEntityReadsDatadogMonitorsAsObjects: before the fix, it panics with interface {} is map[string]interface {}, not int. After the fix, mixed bare and object monitors read as IDs.
  • TestYamlToEntityReadsDatadogMonitorsAsIntegers: includes an ID above 2^53, which reads exactly.
  • TestYamlToEntityRejectsDatadogMonitorWithAlias: string, number, boolean, and empty aliases.
  • TestYamlToEntityRejectsDatadogMonitorWithoutIntegerID: null, missing ID, bare string, non-integer string, fraction, exponent, infinity, out of range, and nested list. Each case checks its own message.
  • TestYamlToEntityRejectsMalformedDatadogApm and TestGetFromDescriptorNamesEntityInParseError.
• gofmt -l, go vet ./..., and golangci-lint run (v2.14.0): clean.
• make testacc: not run locally. CI runs it.

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