Allow to set uid guid when running whatsapp program

Set it using the env variable UID and GUID

Dockerfile

@@ -13,6 +13,12 @@ RUN go build -o /usr/bin/mautrix-whatsapp
 
 FROM alpine:latest
 
+ENV UID=1337 \
+    GID=1337
+
+RUN apk add --no-cache \
+      su-exec
+
 COPY --from=builder /usr/bin/mautrix-whatsapp /usr/bin/mautrix-whatsapp
 COPY --from=builder /etc/ssl/certs/ /etc/ssl/certs
 COPY --from=builder /go/src/maunium.net/go/mautrix-whatsapp/example-config.yaml /opt/mautrix-whatsapp/example-config.yaml

docker-run.sh

@@ -1,5 +1,10 @@
 #!/bin/sh
 
+# Define functions.
+function fixperms {
+	chown -R $UID:$GID /data /opt/mautrix-whatsapp
+}
+
 if [ ! -f /data/config.yaml ]; then
 	cp /opt/mautrix-whatsapp/example-config.yaml /data/config.yaml
 	echo "Didn't find a config file."
@@ -18,4 +23,5 @@ if [ ! -f /data/registration.yaml ]; then
 fi
 
 cd /data
-/usr/bin/mautrix-whatsapp
+fixperms
+exec su-exec $UID:$GID /usr/bin/mautrix-whatsapp