dnscontrol: SPF_BUILDER overflow

If I understand correctly, a TXT record has two maximum lengths: 1024 characters in total and 255 characters per part.

When I create a SPF record of, for example, 750 characters, it is written as "<255 characters>" "<255 characters>" "<240 characters>", but I think this splitting is managed by the API of TransIP, since in preview mode it is displayed as a single record (of 750 characters, which is in fact invalid). When I create a SPF record of 1250 characters the value is splitted in 255 character chunks and later truncated to 1024. This results in an invalid SPF record, since for example the ~all or -all are not at the end, anymore.

While I understand it’s better not to flatten my full SPF record, I think it would be convenient if SPF_BUILDER is able to detect records longer than 1024 characters and splits those similar to the current overflow-feature. For BC and/or situations in which the registrar API is not capable to split at 255 characters, the current behavior should remain, I think.