Metadata fetch bug for new Facebook contacts

[Robi9]

With the union of the Instagram handler with the Facebook handler, an update was carried out in the search for the metadata for new contacts, which ended up influencing the appearance of a bug in the creation of these new contacts, this caused some Facebook contacts to be created without the username.

[norkans7]

I think you mean this change https://github.com/nyaruka/courier/pull/392/files#diff-799bba3fe4dcf9897cf02b0de8b0701a579fdb1799382d109cc97a268662d1d6L653-L657

the method takes a channel in the arguments I think you can use the channel type to do the right thing for each.

Open a PR for that and remember tests