Prepare v1.7.2: fix file naming, improve error messages

[vianneybacoup]

Summary

• Bump version to 1.7.2 (was stuck at 1.7.0 in the v1.7.1 release)
• Fix multi-file output naming: files were named output.csv_0 instead of output_0.csv when using files: N. The index suffix is now inserted before the extension for all formats (CSV, JSON, Parquet)
• Confirm case-insensitive provider lookup: provider names like RANDOM.NUMBER.F64 or Person.Fname already resolve correctly — added explicit tests documenting this behavior
• Improve unknown provider error messages: sub-builders returned empty error strings that got double-wrapped into unreadable BadYAMLFormat("BadYAMLFormat(\"\")") messages. Now each builder reports the unrecognized segment and lists valid options (e.g. Unknown provider: random.float. Expected one of: random.bool, random.date.*, random.number.*, random.string.*). Also fixed FakeLakeError::Display to produce human-readable output instead of Debug formatting

Test plan

• All 302 unit tests pass
• All 16 integration tests pass (including given_seeded_multifile_parquet_should_be_reproducible updated for new naming)
• cargo clippy --all-targets --all-features -- -D warnings clean
• Manual verification: files: 3 produces output_0.csv, output_1.csv, output_2.csv
• Manual verification: invalid provider random.float now shows helpful error with suggestions

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Prepares the v1.7.2 release by correcting multi-file output naming, improving provider-resolution error reporting, and documenting provider lookup behavior (case-insensitive) via tests.

Changes:

• Bump crate version to 1.7.2.
• Adjust multi-file output naming to insert the index before the extension (e.g. output_0.csv).
• Add UnknownProvider error variant + improved Display, propagate errors without double-wrapping, and add case-insensitive provider resolution tests.

Reviewed changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/test.rs	Updates integration test expectations/cleanup for new multi-file Parquet naming.
src/generate/output_format.rs	Implements index-before-extension naming for multi-file generation.
src/errors.rs	Adds UnknownProvider and improves human-readable error formatting.
src/config.rs	Stops re-wrapping provider-builder errors at the column level.
src/providers/provider.rs	Updates unknown-provider handling to include valid options; adds case-insensitive provider resolution test.
src/providers/random/builder.rs	Improves unknown-provider errors for random.* root selection.
src/providers/random/date/builder.rs	Improves unknown-provider errors for date sub-providers.
src/providers/random/number/builder.rs	Improves unknown-provider errors for number sub-providers.
src/providers/random/string/builder.rs	Improves unknown-provider errors for string sub-providers.
src/providers/person/builder.rs	Improves unknown-provider errors for person sub-providers.
src/providers/increment/builder.rs	Improves unknown-provider errors for increment sub-providers.
src/providers/constant/builder.rs	Improves unknown-provider errors for constant sub-providers.
Cargo.toml	Version bump to 1.7.2.
Cargo.lock	Lockfile updated for version bump.

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