R2: EU jurisdiction endpoint

[rubdos]

R2 offers a separate endpoint for EU-jurisdiction-only buckets. I exposed this through a new region variant.

Additionally, this fixes the region comment on Custom and the normal R2 region.

I also just tested this change: the R2-EU endpoint only works if the jurisdiction is forced to EU; otherwise, only the default endpoint works. The default endpoint works in both cases.

---

This change is 

[SheedGuy]

@durch I understand project maintenance happens "every quarter or so", but do you know when you will be back to merge small things like these?

[LockedThread]

@durch I understand project maintenance happens "every quarter or so", but do you know when you will be back to merge small things like these?

^

[brownian-motion-v0[bot]]

Brownian Motion (Brass)

Recommendation: Stop

Summary: PR introduces EU jurisdiction support but lacks clarity on necessity and implementation simplicity. Risk: Medium · Confidence: 70%

Highlights

• Good test coverage
• Clear commit history

Unknowns

• No linked issue
• Missing justification for EU jurisdiction necessity

Next actions

• Keep: existing region structure and tests
• Drop: unnecessary complexity in handling EU jurisdiction
• Add: clear documentation on the necessity of EU endpoint

Reflection questions

• What core assumption underpins this PR's approach?
• How does this change align with the project's longer-term goals?
• Could there be a simpler way to achieve the primary objective here?

[durch]

@rubdos thank you! Will be released in 0.37.*