Display addresses groups
This function returns a string chain containing the list of all the groups the address is a member of.
Examples
*/ Display all the groups the address is member of. The address looked for is the one with the identifier specified as an argument. Ad_numero must be available when the function is used
adr_grp(ad_numero)
*/ Instead of ad_numero, a foreign key referring to it can be used instead. In this case, do_adr1 must be available
adr_grp(do_adr1)