Is it possible to create a SourceURI Column in SQL?
Common practice when modelling compound values like your SourceURI is to split them into the component parts, which have a column each. These are given the types basic to the DBMS i.e. string and UUID.

On retrieval the parts are passed to the application as-is, or concatenated with appropriate punctuation. You may choose to create a calculated column or similar to ensure consistentcy across the application.

Postgres has the composite type construct which may simplify implementation. I have not used it so cannot comment on the implications.