Update the changing database default tablespace (#558)

Update the database default tablespace behavior description to include alter/set command.

Previously the explanation was not quite helpful, as in the user can technically still use the command, previously we said it was not supported which is not true.

Author: Andriciuc

documentation/docs/index/tde-limitations.md

@@ -49,16 +49,17 @@ Limitations of `pg_tde` {{release}}:
 
     The `pg_upgrade` tool does not properly handle the internal encryption keys used by `pg_tde`, which prevents the upgraded cluster from decrypting encrypted relations.
 
-## Changing the database default tablespace
+## `ALTER DATABASE ... SET TABLESPACE`
 
-!!! warning "Changing the database default tablespace is not supported with `pg_tde`"
-    Changing the default tablespace of a database is currently not supported when using `pg_tde`.
+!!! warning "Changing a database tablespace has limited support with `pg_tde`"
+    The `ALTER DATABASE ... SET TABLESPACE` command bypasses PostgreSQL's storage manager (SMGR), which `pg_tde` relies on to enforce encryption.
 
-    This operation bypasses PostgreSQL's storage manager (SMGR), which is not supported by `pg_tde`.
+    - If encrypted objects exist in the database's default tablespace, the operation is refused.
+    - If no encrypted objects are present in the default tablespace, the operation is allowed.
 
-    As a safeguard, `pg_tde` blocks the operation if encrypted objects are detected in the default tablespace.
+    Only objects in the default tablespace are checked. Objects in other tablespaces are not evaluated by `pg_tde`.
 
-    Objects located outside the default tablespace are not affected by this command.
+    To move encrypted tables individually, use `ALTER TABLE ... SET TABLESPACE`, which operates through SMGR and is compatible with `pg_tde`.
 
 ## Currently unsupported WAL tools