[sabir-akhadov-localstack]

Snowflake's ALTER EXTERNAL VOLUME did not parse:

ALTER EXTERNAL VOLUME my_vol ADD STORAGE_LOCATION = (
    NAME = 'loc2' STORAGE_PROVIDER = 'S3' STORAGE_BASE_URL = 's3://bucket2/');
ALTER EXTERNAL VOLUME my_vol SET ALLOW_WRITES = TRUE;
ALTER EXTERNAL VOLUME my_vol REMOVE STORAGE_LOCATION 'loc1';

This adds an AlterExternalVolume statement with the three documented operations (ADD STORAGE_LOCATION, SET ALLOW_WRITES, REMOVE STORAGE_LOCATION). The added storage location reuses the same generic KeyValueOptions parsing as CREATE EXTERNAL VOLUME. All statements round-trip.

See the Snowflake ALTER EXTERNAL VOLUME docs.

Split out of #2397 per review feedback, alongside the CREATE/DROP (#2475), DESC (#2472), and SHOW (#2473) PRs.

Stacked on #2475 (it reuses the storage-location parsing helper introduced there) — only the last commit is new. Kept as a draft until #2475 merges, then it will be rebased.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 87.30159% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.32%. Comparing base (23e9e88) to head (6cc4ca4).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/dialect/snowflake.rs	88.88%	0 Missing and 8 partials ⚠️
src/ast/mod.rs	87.75%	1 Missing and 5 partials ⚠️
src/ast/spans.rs	50.00%	1 Missing ⚠️
src/parser/mod.rs	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2474      +/-   ##
==========================================
+ Coverage   82.30%   82.32%   +0.02%     
==========================================
  Files          42       42              
  Lines       35294    35419     +125     
  Branches    35294    35419     +125     
==========================================
+ Hits        29047    29160     +113     
  Misses       2690     2690              
- Partials     3557     3569      +12     

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[sabir-akhadov-localstack]

Rebased on latest main, so the conflicts are resolved and the needs rebasing label can be dropped. This one is stacked on #2475 (CREATE/DROP EXTERNAL VOLUME), so it's best reviewed after that one. @LucaCappelletti94, no rush, whenever you get to it.