Support PUID and PGID environment variables

[IslandJohn]

Many Docker containers allow setting the PUID and PGID environment variables so that the entry points shed their default 0:0 permissions. The gphotos-sync container setup currently ignores these. Please consider adding support for them.

[gilesknap]

Hi @IslandJohn

If I understand the use of these correctly then I believe we already have a solution for this. Take a look at this and see if it meets your requirement #279 (comment)

[IslandJohn]

Thanks, yes that's an option, it's just "less standard" on a Synology packing of Docker and I've been using env. vars where possible. Usually through the env vars the Dockerfile has adduser and shed the root permissions at startup.

[gilesknap]

Ok that sounds easy enough. I'll take a look soon.