Hard coded version and handling of errors gracefully in `get_sessionid`

[surfer190]

Should the vcd version rather come from configuration? You get a 406 on a later version of vcd with the below error message when the version is set to 5.1.

message="The request has invalid accept header: . Supported API versions are: [32.0, 31.0, 30.0, 29.0, 28.0 [D], 27.0 [D], 26.0 [D], 25.0 [D], 24.0 [D], 23.0 [D], 22.0 [D], 21.0 [D], 20.0 [D]] ([D] indicates deprecated versions)"

Also is adding @system wise to do here? What if a user sets the config to xxxx@system in the configuration? A warning should perhaps be added to the configuration schema in config.schema.yaml

Also perhaps we should catch anything that isn't a 200 status code here and give a nicer looking error message?

    def get_sessionid(self):
        url = 'https://%s/api/sessions' % self.vcd_host
        headers = {'Accept': 'application/*+xml;version=5.1'}
        p = requests.post(url, headers=headers, auth=(self.vcd_user +  # noqa: W504
                                                      "@SYSTEM", self.vcd_pass),
                          verify=self.vcd_ssl)
        self.vcd_auth = p.headers['x-vcloud-authorization']

        return self.vcd_auth

[nmaludy]

@surfer190 Sounds like there are a few things here, let me break them down and let's talk about them one at a time.

1. Hard coded version number: Yes, it does look like the version is hard coded here https://github.com/StackStorm-Exchange/stackstorm-vcd/blob/master/actions/lib/vcd.py#L53 . Adding the version to the config schema makes sense to me! Would you mind trying to craft a PR for this (i don't have VCD to test with)?

2. Hard coded domain: Yes, it does look like the domain of @SYSTEM is hard coded here: https://github.com/StackStorm-Exchange/stackstorm-vcd/blob/master/actions/lib/vcd.py#L55 . Similar to the version number, i'm thinking this should probably be part of the config with a default value of SYSTEM and the code can insert the @ itself. Alternatively we could expect the user to be fully qualified and append @system if there is no @ character in the user.

[surfer190]

@nmaludy Since the module supports the use of different vcd instances, it would make sense for the api version to be set per instance - so alongside hostname, username and password.

I feel like the solution of appending the @system if no @ is present in the string is a good one.

These changes could break existing workflows and actions, they would need to update their config. Is that acceptable?