Update PrimaryKey deprecation warning (piccolo-orm#176)

* Update PrimaryKey deprecation warning

* tweaks to deprecation warning

Co-authored-by: Daniel Townsend <[email protected]>

Author: tonybaloney

piccolo/columns/column_types.py

@@ -529,8 +529,11 @@ def __init__(self, **kwargs) -> None:
         kwargs.update({"primary_key": True, "index": False})
 
         colored_warning(
-            "`PrimaryKey` is deprecated and "
-            "will be removed in future versions.",
+            "`PrimaryKey` is deprecated and will be removed in future "
+            "versions. Use `UUID(primary_key=True)` or "
+            "`Serial(primary_key=True)` instead. If no primary key column is "
+            "specified, Piccolo will automatically add one for you called "
+            "`id`.",
             category=DeprecationWarning,
         )