Shared secret support, fix COMPOSE_FILE format

.env.sample

@@ -7,23 +7,29 @@ SECRET_ADMIN_PASSWORD_VERSION=v1
 
 DEFAULT_LOCALES="fr_FR fr_FR.UTF-8 en_GB en_GB.UTF-8 en_US en_US.UTF-8 nl_NL nl_NL.UTF-8"
 
+COMPOSE_FILE="compose.yml"
+
 # Custom R version
-#COMPOSE_FILE="compose.yml:compose.version.yml"
+#COMPOSE_FILE="$COMPOSE_FILE:compose.version.yml"
 #R_VERSION=3.6.3
 
 # MSSQL driver
 MSSQL_ENABLED="1"
 
 # OpenID Connect (SSO)
-#COMPOSE_FILE="compose.yml:compose.oidc.yml"
+#COMPOSE_FILE="$COMPOSE_FILE:compose.oidc.yml"
 #OIDC_ENABLED=1
 #OIDC_CLIENT_ID=
 #OIDC_ISSUER_URL=
 #SECRET_OIDC_CLIENT_SECRET=v1
 
 # Keycloak integration
-#COMPOSE_FILE="compose.yml:compose.keycloak.yml"
+#COMPOSE_FILE="$COMPOSE_FILE:compose.keycloak.yml"
 #KEYCLOAK_ENABLED=1
 #KEYCLOAK_CLIENT_ID=
 #KEYCLOAK_CLIENT_TOKEN_URL=
 #SECRET_KEYCLOAK_CLIENT_SECRET=v1
+
+# Shared secret
+#COMPOSE_FILE="$COMPOSE_FILE:compose.keycloak-sharedsecret.yml"
+#SHARED_SECRET_NAME=keycloak_rstudio_client_secret

compose.keycloak-sharedsecret.yml

@@ -0,0 +1,7 @@
+---
+version: "3.8"
+
+secrets:
+  keycloak_client_secret:
+    name: ${SHARED_SECRET_NAME}
+    external: true