Add a reference

Author: javiereguiluz

components/uid.rst

@@ -113,6 +113,8 @@ sortable (like :ref:`ULIDs <ulid>`). It's more efficient for database indexing
     It's recommended to use UUIDv7 instead of UUIDv6 because it provides
     better entropy.
 
+.. _uid-uuid-v7:
+
 **UUID v7** (UNIX timestamp)
 
 Generates time-ordered UUIDs based on a high-resolution Unix Epoch timestamp
@@ -347,10 +349,10 @@ entity primary keys::
 .. caution::
 
     Using UUIDs as primary keys is usually not recommended for performance reasons:
-    indexes are slower and take more space (because UUIDs in binary format take 128 bits
-    instead of 32/64 bits for auto-incremental integers) and the non-sequential nature of
-    UUIDs fragments indexes. UUID v7 is the only variant that solves the fragmentation
-    issue (but the index size issue remains).
+    indexes are slower and take more space (because UUIDs in binary format take
+    128 bits instead of 32/64 bits for auto-incremental integers) and the non-sequential
+    nature of UUIDs fragments indexes. :ref:`UUID v7 <uid-uuid-v7>` is the only
+    variant that solves the fragmentation issue (but the index size issue remains).
 
 When using built-in Doctrine repository methods (e.g. ``findOneBy()``), Doctrine
 knows how to convert these UUID types to build the SQL query