Fix warnings in Dockerfile

Fix warning related to obsolete/deprecated
Dockerfile syntax.

Signed-off-by: Andreia Ocanoaia <andreia.ocanoaia@gmail.com>

Author: andreia-oca

dockerfile/dropbox.Dockerfile

@@ -3,19 +3,21 @@
 FROM ubuntu:22.04
 
 # Maintainer
-LABEL maintainer "Alexander Graf <alex@otherguy.io>"
+LABEL maintainer="Alexander Graf <alex@otherguy.io>"
 
 # Build arguments
-ARG VCS_REF=master
+ARG VCS_REF=main
+ARG VERSION=""
 ARG BUILD_DATE=""
 
 # http://label-schema.org/rc1/
-LABEL org.label-schema.schema-version "1.0"
-LABEL org.label-schema.name           "Dropbox"
-LABEL org.label-schema.build-date     "${BUILD_DATE}"
-LABEL org.label-schema.description    "Standalone Dropbox client"
-LABEL org.label-schema.vcs-url        "https://github.com/otherguy/docker-dropbox"
-LABEL org.label-schema.vcs-ref        "${VCS_REF}"
+LABEL org.label-schema.schema-version="1.0"
+LABEL org.label-schema.name="Dropbox"
+LABEL org.label-schema.version="${VERSION}"
+LABEL org.label-schema.build-date="${BUILD_DATE}"
+LABEL org.label-schema.description="Standalone Dropbox client"
+LABEL org.label-schema.vcs-url="https://github.com/otherguy/docker-dropbox"
+LABEL org.label-schema.vcs-ref="${VCS_REF}"
 
 # Required to prevent warnings
 ARG DEBIAN_FRONTEND=noninteractive
@@ -32,21 +34,16 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
  && rm -rf /var/lib/apt/lists/*
 
 # Create user and group
-RUN mkdir -p /opt/dropbox /opt/dropbox/.dropbox /opt/dropbox/Dropbox \
+RUN mkdir -p /opt/dropbox \
  && useradd --home-dir /opt/dropbox --comment "Dropbox Daemon Account" --user-group --shell /usr/sbin/nologin dropbox \
  && chown -R dropbox:dropbox /opt/dropbox
 
 # Set language
-ENV LANG     "en_US.UTF-8"
-ENV LANGUAGE "en_US.UTF-8"
-ENV LC_ALL   "en_US.UTF-8"
-
-# Generate locales
-RUN sed --in-place '/en_US.UTF-8/s/^# //' /etc/locale.gen \
- && locale-gen
+ENV LANG="C.UTF-8"
+ENV LC_ALL="C.UTF-8"
 
 # Change working directory
-WORKDIR /opt/dropbox/Dropbox
+WORKDIR /opt/dropbox
 
 # Not really required for --net=host
 EXPOSE 17500