Use env interpolation in config (#826)

docker/Dockerfile

@@ -11,6 +11,21 @@ RUN wget http://github.com/begriffs/postgrest/releases/download/v${POSTGREST_VER
     mv postgrest /usr/local/bin/postgrest && \
     rm postgrest-${POSTGREST_VERSION}-ubuntu.tar.xz
 
+COPY postgrest.conf /etc/postgrest.conf
+
+
+ENV PGRST_DB_URI= \
+    PGRST_DB_SCHEMA=public \
+    PGRST_DB_ANON_ROLE= \
+    PGRST_DB_POOL=100 \
+    PGRST_SERVER_HOST=*4 \
+    PGRST_SERVER_PORT=3000 \
+    PGRST_SERVER_PROXY_URL= \
+    PGRST_JWT_SECRET= \
+    PGRST_SECRET_IS_BASE64=false \
+    PGRST_MAX_ROWS= \
+    PGRST_PRE_REQUEST=
+
 # PostgREST reads /etc/postgrest.conf so map the configuration
 # file in when you run this container
 CMD exec postgrest /etc/postgrest.conf