Add support for ltree data type

[kvch]

Description

This PR adds support for the ltree data type: https://www.postgresql.org/docs/current/ltree.html

It came up during the investigation into cube data type.

Type of Change

Please select the relevant option(s):

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🔧 Refactoring (no functional changes)
• ⚡ Performance improvement
• 🧪 Test coverage improvement
• 🔨 Build/CI changes
• 🧹 Code cleanup

Changes Made

• internal/postgres/pg_utils.go — add {name: "ltree", register: registerWithCodec("ltree", pgtype.TextCodec{})} to extensionTypes so source reads return ltree values as strings.
• pkg/wal/processor/postgres/postgres_wal_dml_adapter.go — add "ltree": {} to textOnlyCopyTypes so bulk ingest dispatches affected batches to Txn.CopyFromText.

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• All existing tests pass

Checklist

• Code follows project style guidelines
• Self-review completed
• Code is well-commented
• Documentation updated where necessary

[exekias]

This will always byte us with every new/missing data type, I wonder if there could be a generic way to copy "anything"

[kvch]

This will always byte us with every new/missing data type, I wonder if there could be a generic way to copy "anything"

Unfortunately, pgx Copy functionality has some limitations when it comes to parsing custom data types. I will look into handling these issues more gracefully and/or finding a way to parse the data in a more robust manner.

[github-actions]

Merging this branch will not change overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/xataio/pgstream/internal/postgres	29.31% (ø)
github.com/xataio/pgstream/pkg/stream/integration	0.00% (ø)
github.com/xataio/pgstream/pkg/wal/processor/postgres	79.34% (ø)

---

Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/xataio/pgstream/internal/postgres/pg_utils.go	47.37% (ø)	114	54	60
github.com/xataio/pgstream/pkg/wal/processor/postgres/postgres_wal_dml_adapter.go	94.64% (ø)	168	159	9

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/xataio/pgstream/pkg/stream/integration/snapshot_pg_integration_test.go