Add support for setting retention period using RETAIN syntax

[CGodiksen]

Closes #343 by changing the parser to support the syntax VACUUM table_name RETAIN num_seconds. Note that RETAIN is optional.

The PR also removes the previous method for setting the retention period which was through the environment variable MODELARDBD_RETENTION_PERIOD_IN_SECONDS and the configuration retention_period_in_seconds. This method was removed to avoid confusion between the two ways to set the retention period and since the setting was also only supposed to be used in the server (modelardbd). It could have been kept in the server but this might cause confusion on how it is handled in the manager and Operations API.

[Copilot]

Pull Request Overview

This PR adds support for setting retention periods in VACUUM commands using the RETAIN num_seconds syntax, while removing the previous environment variable-based configuration approach. The changes enable users to specify retention periods directly in SQL rather than through server configuration.

Key changes:

• Extended the VACUUM SQL parser to support optional RETAIN num_seconds syntax
• Updated all vacuum operations to accept an optional retention period parameter
• Removed environment variable and configuration-based retention period settings

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
crates/modelardb_types/src/flight/protocol.proto	Removed retention_period_in_seconds from Configuration protobuf
crates/modelardb_storage/src/parser.rs	Extended VACUUM parser to support RETAIN syntax with validation
crates/modelardb_storage/src/delta_lake.rs	Updated vacuum_table to accept optional retention period
crates/modelardb_server/tests/integration_test.rs	Updated tests to use new VACUUM syntax instead of configuration
crates/modelardb_server/src/remote.rs	Updated FlightService to pass retention period from parsed SQL
crates/modelardb_server/src/context.rs	Updated vacuum_table method signature and removed configuration usage
crates/modelardb_server/src/configuration.rs	Removed retention period fields and methods from ConfigurationManager
crates/modelardb_manager/src/remote.rs	Updated manager to handle new vacuum syntax and parameter passing
crates/modelardb_embedded/src/operations/mod.rs	Updated Operations trait vacuum method signature
crates/modelardb_embedded/src/operations/data_folder.rs	Removed environment variable usage, updated vacuum implementation
crates/modelardb_embedded/src/operations/client.rs	Updated client vacuum to construct SQL with RETAIN syntax
crates/modelardb_embedded/src/capi.rs	Updated C API to accept retention period parameter
crates/modelardb_embedded/bindings/python/tests/test_operations.py	Updated Python tests to use new vacuum API
crates/modelardb_embedded/bindings/python/modelardb/operations.py	Updated Python bindings to support retention period parameter

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