Re-enable importing from dumps v1

[dureuill]

Pull Request

Related issue

Fixes #2985

What does this PR do?

User standpoint

• Allows importing dumps version 1 (exported with Meilisearch <=v0.20) to modern-day Meilisearch
• Tasks of type "Customs" are skipped, with a warning
• Tasks of status "enqueued" are skipped, with a warning
• The "WordsPosition" ranking rule is skipped when encountered in the ranking rules, with a warning.

After an import from a v1 dump, it is recommended that a user checks each index and its settings.

Implementation standpoint

• Add a dump v1 reader based on the one by @irevoire
• Add a v1_to_v2 compatibility layer based on the v2_to_v3 one
  • as v2 requires UUIDs, the v1 indexes are mapped to UUIDs built from their position in the metada file: the first index is given UUID all zeroes, the second one UUID 00000000-0000-0000-0000-000000000001, and so on... This should have no bearing on the final indexes because v6 is not using UUIDs, but this allows us to correctly identify which tasks belong to which index.
• Modify the v2_to_v3 compatibility layer to account for the fact that the reader can actually be a v1_to_v2 compat layer
• Make some base dump types Clone
• impl Display for v2::settings::Criterion

PR checklist

Please check if your PR fulfills the following requirements:

• Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
• Have you read the contributing guidelines?
• Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!

[irevoire]

Hey, it looks super good.

Could you add one test at the bottom of dump/src/reader/mod.rs that imports our dump v1 through all our compat layers, please? 😁

[dureuill]

Could you add one test at the bottom of dump/src/reader/mod.rs that imports our dump v1 through all our compat layers, please? 😁

Oh sorry I didn't write a message to specify, but I did that.

Also I detailed some of the quirks of the current implementation, format-wise, in #2985 (comment)

[irevoire]

Nice, we're good to me!

bors merge

[bors]

🕐 Waiting for PR status (GitHub check) to be set, probably by CI. Bors will automatically try to run when all required PR statuses are set.

[irevoire]

bors merge

[bors]

Stopped waiting for PR status (GitHub check) without running due to duplicate requests to run. You may check Bors to see that this PR is included in a batch by one of the other requests.

[bors]

Build succeeded:

• Run Clippy
• Run Rustfmt
• Run tests in debug
• Tests on macos-latest
• Tests on ubuntu-18.04
• Tests on windows-latest