merge to stable-25-2 YDBDOCS-1245 add docs for import / export (ch 1)

[GrigoriyPA]

Changelog entry

Added docs for import / export (ch 1)

Changelog category

• Documentation (changelog entry is not required)

Description for reviewers

PRs from main:

• New documentation on formatting settings for reading from s3 #15970

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🟢 2025-09-12 11:30:03 UTC The validation of the Pull Request description is successful.

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Warnings (1)

⚠️ ru/concepts/federated_query/s3/external_data_source.md: 102: MD009 / no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]

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⚪ 2025-09-12 11:32:28 UTC Pre-commit check linux-x86_64-relwithdebinfo for fddb52b has started.
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⚫ 2025-09-12 11:34:27 UTC Check cancelled

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⚪ 2025-09-12 11:35:49 UTC Pre-commit check linux-x86_64-release-asan for 7320fe9 has started.
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⚪ 2025-09-12 11:38:23 UTC ya make is running...
🟢 2025-09-12 11:38:29 UTC Tests successful.

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
0	0	0	0	0	0

🟢 2025-09-12 11:38:35 UTC Build successful.

[github-actions]

⚪ 2025-09-12 11:36:51 UTC Pre-commit check linux-x86_64-relwithdebinfo for 7320fe9 has started.
⚪ 2025-09-12 11:36:54 UTC Artifacts will be uploaded here
⚪ 2025-09-12 11:39:12 UTC ya make is running...
🟢 2025-09-12 11:39:17 UTC Tests successful.

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
0	0	0	0	0	0

🟢 2025-09-12 11:39:25 UTC Build successful.

[github-actions]

✅ Documentation build

Revision built successfully
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[CyberROFL]

lgtm