Give more information on a failed configuration validation.

[Fryguy]

https://bugzilla.redhat.com/show_bug.cgi?id=1558031

@gtanzillo Please review

@abellotti This also gives you a proper exception class that you can rescue in the API side so that you can return a 400 error instead of a 500 error.

[Fryguy]

Before:

RuntimeError: configuration invalid

After

Vmdb::Settings::ConfigurationInvalid: authentication-mode: authentication mode, nil, is invalid. Should be one of: database, httpd, ldap, ldaps, amazon, none

[miq-bot]

Checked commit Fryguy@e089d49 with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
5 files checked, 0 offenses detected
Everything looks fine. 🍰

[Fryguy]

Here's what it looks like with manageiq-api-client

[7] pry(main)> client.patch("servers/21000000000002/settings") { {"authentication" => {"bind_timeout" => 123 }} }
RuntimeError: authentication-mode: authentication mode, nil, is invalid. Should be one of: httpd, database, ldap, ldaps, amazon, none
from (manageiq-api-client-0.3.0) lib/manageiq/api/client/connection.rb:108:in `check_response'
(manageiq-api-client-0.3.0) lib/manageiq/api/client/connection.rb:102:in `send_request'
(manageiq-api-client-0.3.0) lib/manageiq/api/client/connection.rb:39:in `patch'
(manageiq-api-client-0.3.0) lib/manageiq/api/client/client.rb:65:in `patch'
(pry):7:in `<main>'

[gtanzillo]

👍