partitioningprocessor: implement logs partitioning

[axw]

This PR implements the OTTL-based partitioning logic for logs. It is not wired up to the processor yet.

Relates to open-telemetry/opentelemetry-collector-contrib#39199

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📝 Walkthrough

Walkthrough

The PR implements log partitioning by OTTL expressions: Config was changed to include a TODO (and Validate() removed), and a new PartitionKeyConfig type was added. A parser (parser.go) builds OTTL parsers for resource/scope/log contexts and constructs a logs partitioner. A partitioner implementation (partitioner.go) groups plog.Logs by evaluated string keys. Extensive tests were added for parser, partitioning behavior, key formatting/order, deduplication, schema preservation, and processor capabilities. go.mod was updated to add an OTTL dependency and related indirect modules.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

• 🛠️ Update Documentation: Commit on current branch
• 🛠️ Update Documentation: Create PR

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 golangci-lint (2.11.4)

level=error msg="[linters_context] typechecking error: pattern ./...: directory prefix . does not contain main module or its selected dependencies"

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[axw]

@CodeRabbit review

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@processor/partitioningprocessor/partitioner.go`:
- Around line 120-123: The evaluateScope method in scopeLogsPartitioner uses
ottlscope.NewTransformContextPtr(sl.Scope(), rl.Resource(), sl), which passes
the scope as the single schema URL item so GetScopeSchemaURLItem() and
GetResourceSchemaURLItem() return the same schemaURLItem causing
resource.schema_url to read the scope schema URL; update evaluateScope (or the
context creation) to provide both resource and scope schema URL items separately
(or detect and reject expressions that reference both schema URLs) so
resource.schema_url resolves to the resource's schema URL, and add a unit test
exercising differing scope vs resource schema URLs to ensure
evaluateStringExpressions (called from evaluateScope) behaves correctly;
reference functions/types: evaluateScope, scopeLogsPartitioner,
ottlscope.NewTransformContextPtr, evaluateStringExpressions, and the
resource.schema_url / scope.schema_url getters.

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Fix all unresolved CodeRabbit comments on this PR:

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

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Run ID: fa45cd84-8909-41eb-bba4-6d35fa22365d

📥 Commits

Reviewing files that changed from the base of the PR and between ac20366 and 3b3e009.

⛔ Files ignored due to path filters (1)

• processor/partitioningprocessor/go.sum is excluded by !**/*.sum

📒 Files selected for processing (7)

• processor/partitioningprocessor/config.go
• processor/partitioningprocessor/go.mod
• processor/partitioningprocessor/parser.go
• processor/partitioningprocessor/parser_test.go
• processor/partitioningprocessor/partitioner.go
• processor/partitioningprocessor/partitioner_test.go
• processor/partitioningprocessor/processor_test.go

✅ Files skipped from review due to trivial changes (2)

• processor/partitioningprocessor/processor_test.go
• processor/partitioningprocessor/parser.go

🚧 Files skipped from review as they are similar to previous changes (1)

• processor/partitioningprocessor/go.mod