Add create Git backed automation domain

[jvlcek]

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1600961

This PR, along with PR manageiq-ui-classic/5416 will provide the support to allow the API to be used to create a Git backed automation domain.

Steps for Testing/QA [Optional]

Create a GIT based automate domain repository.

Use the API to issue a POST command to `/api/automate_domains with data similar to:
{
"git_url": "https://gitlab.exampledomain.com/gitlab_repo/AwesomeDomain",
"ref_type": "branch",
"ref_name": "master",
}

e.g.:

cat action_create_from_git
{
"git_url": "https://gitlab.exampledomain.com/gitlab_repo/AwesomeDomain",
"ref_type": "branch",
"ref_name": "master",
}
curl -k --user admin:SECRET_PASSWORD -i -X POST -H "Accept: application/json" -d @action_create_from_git https://my-miq-host/api/automate_domains

[jvlcek]

@miq-bot add_label enhancement
@miq-bot add_label bug
@miq-bot add_label hammer/no

[jvlcek]

@mkanoor Please review

[jvlcek]

@Fryguy, @abellotti and @mkanoor Please review.

[abellotti]

Looks good Joe, a couple of questions/minor changes.

[abellotti]

raise BadRequestError, "Git owner ...."

[jvlcek]

@abellotti Got it.

[miq-bot]

Some comments on commits jvlcek/manageiq-api@7dc2970~...7b07dd3

spec/requests/automate_domains_spec.rb

• ⚠️ - 114 - Detected expect_any_instance_of. This RSpec method is highly discouraged, please only use when absolutely necessary.

[miq-bot]

Checked commits jvlcek/manageiq-api@7dc2970~...7b07dd3 with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
2 files checked, 1 offense detected

app/controllers/api/automate_domains_controller.rb

• ❗ - Line 23, Col 7 - Style/RescueStandardError - Avoid rescuing without specifying an error class.

[jvlcek]

Note: This PR relies on manageiq-ui-classic/5416

[abellotti]

LGTM!! Thanks @jvlcek for the API enhancement. 👍 @Fryguy and @mkanoor can you lend some 👀 here. Thanks.

[gtanzillo]

Looks good 👍

[ghost]

Fixes #354