external table support

[babaktey]

Describe the feature

this feature is to allow the dbt users to add the support of the teradata FOREIGN TABLE as external source/seed.
this example comes from the MS Synapse implementation :
https://github.com/dbt-labs/dbt-external-tables/blob/main/sample_sources/synapse.yml

[sunilkmallam]

Thank you for your request, @babaktey.

We have this feature in our backlog. We'd send you an update, once it's goes live.

FYI, @VarunSharma15 and @tallamohan