add koji/addingusers and koji/building

docs/koji/addingusers.md

+# Adding users to koji
+
+* Adding users to koji and granting them access to repositories requires admin privileges
+* This can only be done by other admins
+
+## Adding a user
+
+You can add a user with: `koji add-user --principal=<username>@CERN.CH <username>`
+
+!!! danger "Important!"
+
+	* Do NOT forget the @CERN.CH from the user principal
+	* If you do, the user won't be able to log in manual database modification is required to fix the mistake
+
+* Note: If you get `GenericError: user already exists: user` you can safely ignore it
+
+## Granting build permissions
+
+* First add the user as documented above. Then do `koji grant-permission build <username>`
+* 'build' is required to do basically anything useful in koji
+
+## Granting admin permissions
+
+* First add the user as documented above. Then do `koji grant-permission admin <username>`
+
+!!! danger "Important!"
+	Admin accounts should only be granted to service managers of the koji service