db-doc: group_user description

db_structure.xml

@@ -446,11 +446,16 @@
 	</table>
 
 	<table>
-
+		<!--
+		Stores which groups have which users as members in an n:m relationship.
+		 - Maps group id (gid) to a set of users (uid)
+		 - Maps user id (uid) to a set of groups (gid) (but without index)
+		-->
 		<name>*dbprefix*group_user</name>
 
 		<declaration>
 
+			<!-- Foreign Key groups::gid -->
 			<field>
 				<name>gid</name>
 				<type>text</type>
@@ -459,6 +464,7 @@
 				<length>64</length>
 			</field>
 
+			<!-- Foreign Key users::uid -->
 			<field>
 				<name>uid</name>
 				<type>text</type>