[feature] Provide method to manage S3 users via the charm

[Nick Niehoff]

Radosgw provides an s3 endpoint and as per the charm documentation users can be created using the radosgw-admin user create function to create a user and get the S3 access_key and secret_key. For managed environments that need a method to rebuild on demand/disaster we need a way to at least maintain a list of users in juju that will need to be recreated. Here is the process to test S3 today:

I created a ubuntu user from ceph-mon/0, with:

$ sudo radosgw-admin user create --uid="ubuntu" --display-name="Ubuntu Ceph"

That has generated the access_key and secret_key to be used with S3:

"keys": [
{
"user": "ubuntu",
"access_key": "B7OLQ0W7EG8N7YBP4BFB",
"secret_key": "Ukp18Fs2FGeXPLAHiIAlvWczWx9TMpM961HpEwiQ"
}
],

--
To test S3 access, I installed the s3cmd with:

$ sudo apt install -y s3cmd

--
Once installed, I have generated a .cfg file to be tailored, and point out to our ceph-rgw Unit. For that:

$ s3cmd --configure -c s3test.cfg

The s3test.cfg file was edited, to reflect the access_key, secret_key, host_base and host_bucket information. For our test, I had changed use_https to False.

https://pastebin.canonical.com/p/gQqpBHjpBD/plain/

--
At last, I could use the commands from s3cmd, with:

$ s3cmd -c s3test.cfg <command>