feat: partition format

[kevthompson]

Description

Replacing the limited s3_partition option with a dynamic s3_partition_format option to allow custom filenames. Allows users to define their own partition formats (e.g. removing the "year=" strings or partitioning weekly).

This is a breaking change, I created this as a new input and removed the s3_partition so anyone that was on hourly partitions won't accidentally upgrade and change their file formats. The default format still points to the same location.

Also fixed a bug where not specifying a prefix would create an empty directory in the bucket.

Link to tracking issue

Fixes #37915
Fixes #37503

Testing

Test cases all passing

Tested against personal S3 bucket

• when no value is given it matches the current default => s3://test-otel-s3-exporter/year=2025/month=02/day=23/hour=22/minute=34/logs_235895800.json
• custom path '%Y/%m/%d/%H/%M' => s3://test-otel-s3-exporter/2025/02/23/22/34/logs_216971670.json
• custom path with prefix => s3://test-otel-s3-exporter/baz/2025/02/23/22/33/logs_134704167.json

Documentation

Updated README with new s3_partition_format input & removed the s3_partition entry. Added an extra example config with a custom partition format.

[atoulme]

Changes make sense, it's an alpha exporter, maybe we can afford this breaking change.

[kevthompson]

Validated against my personal S3 bucket & fixed the link the workflows were complaining about, all working as expected

[atoulme]

CI fails:

go.mod/go.sum deps changes detected, please run "make gotidy" and commit the changes in this PR.

[atoulme]

I am kicking the build, please hold off merging main, I have to kick the build off every time you do :)