add validation check against duplicated filter slugs
add validation check against duplicated filter slugs

qedsoftware/commcare-hq,puttarajubr/commcare-hq,qedsoftware/commcare-hq,puttarajubr/commcare-hq,dimagi/commcare-hq,puttarajubr/commcare-hq,dimagi/commcare-hq,puttarajubr/commcare-hq,dimagi/commcare-hq,dimagi/commcare-hq,qedsoftware/commcare-hq,qedsoftware/commcare-hq,qedsoftware/commcare-hq,dimagi/commcare-hq