add dbt-postgres target for historical releases of dbt-postgres

docker/Dockerfile

@@ -37,6 +37,18 @@ ENTRYPOINT ["dbt"]
 RUN python -m pip install --no-cache-dir "dbt-core @ git+https://github.com/dbt-labs/dbt-core@${commit_ref}#subdirectory=core"
 
 
+FROM base as dbt-postgres
+
+ARG commit_ref=main
+
+HEALTHCHECK CMD dbt --version || exit 1
+
+WORKDIR /usr/app/dbt/
+ENTRYPOINT ["dbt"]
+
+RUN python -m pip install --no-cache-dir "dbt-postgres @ git+https://github.com/dbt-labs/dbt-core@${commit_ref}#subdirectory=plugins/postgres"
+
+
 FROM dbt-core as dbt-third-party
 
 ARG dbt_third_party