docs: update UUID recommendation to v7 for better database performance

[OlivierBarbier]

Thanks for the documentation reference!

I noticed the linked 2015 blog post advocates for UUIDv4, but doesn't mention the database performance implications that have become better understood since then.

UUIDv4's random nature can be detrimental to database performance: when inserted as a primary key into B-tree indexes (like MySQL InnoDB or PostgreSQL), random UUIDs can fall into any position in the index. This causes frequent page splits, index fragmentation, slower writes, and poor cache utilization.

Would you be open to recommending UUIDv7 instead? It maintains the benefits of UUIDs while avoiding these performance issues thanks to its time-ordered structure.