add url import subcommand

[ecordell]

Adds a zed import <url> command to import schema and relationships to a spicedb instance.

It can read directly from a file or url if it contains the devtools export format

It also has hard-coded support for importing from the authzed playground, gists, and pastebin.

Examples:

# from a gist
$ zed import https://gist.github.com/ecordell/8e3b613a677e3c844742cf24421c08b6

# from a playground link
$ zed import https://play.authzed.com/s/iksdFvCtvnkR/schema

# from pastebin
$ zed import https://pastebin.com/8qU45rVK

# from a devtools instance
$ zed import https://localhost:8443/download

# from a local file
$ zed import file:///Users/evan/Downloads/authzed-x7izWU8_2Gw3.yaml

# only schema 
$ zed import --relationships=false file:///Users/evan/Downloads/authzed-x7izWU8_2Gw3.yaml

# only relationships 
$ zed import --schema=false file:///Users/evan/Downloads/authzed-x7izWU8_2Gw3.yaml

# trace to see what relationships are written
$ zed import --log-level=trace file:///Users/evan/Downloads/authzed-x7izWU8_2Gw3.yaml

Note that the playground import relies on urls of the form https://play.authzed.com/s/iksdFvCtvnkR/download returning the full developer api download output

Fixes #24

[josephschorr]

Should probably have json mode to match the other commands

[ecordell]

There's not really output for this command aside from the log messages (which already detect if it's a tty and switch to json if not)

[josephschorr]

LGTM

[josephschorr]

LGTM