[Feature] Add missing Resources/Endpoints Q1/2022

[Kjarrigan]

It's been a while since someone worked on this project so there is a bit of a gap between what you can do through the API and through this gem, so we should go through the API and check what is actually missing and then create issues to close the gaps (e.g. LoadBalancer are missing as well as PlacementGroups)

So all unchecked entries are not yet checked for differences - based on the official docs

• Actions
• Certificates missing [Feature] Add Certificates #26
• Certificate Actions missing [Feature] Add Certificates #26
• Datacenters
• Firewalls missing [Feature] Add Firewalls #25
• Firewall Actions missing [Feature] Add Firewalls #25
• Floating IPs - field:labels missing [Feature] Label support #12
• Floating IP Actions
• Images - field:labels missing [Feature] Label support #12
• Image Actions - get action(s) missing [Enhancement] Add missing fields / endpoints to Images + Servers #30
• ISOs
• Load Balancers missing [Feature] Add LoadBalancers and -Types #29
• Load Balancer Actions missing [Feature] Add LoadBalancers and -Types #29
• Load Balancer Types missing [Feature] Add LoadBalancers and -Types #29
• Locations
• Networks - field:labels missing [Feature] Label support #12 [Feature] Add Certificates #26
• Network Actions get action(s) + change_ip_range missing
• Placement Groups missing [Feature] Add PlacementGroups #27
• Pricing missing [Feature] Add Pricing #28
• Servers - field:labels missing [Feature] Label support #12 + get-metrics missing
• Server Actions - change_dns_ptr missing [Enhancement] Add missing fields / endpoints to Images + Servers #30
• Server Types
• SSH Keys - field:labels missing [Feature] Label support #12
• Volumes - field:labels missing [Feature] Label support #12
• Volume Actions

[Kjarrigan]

Move to Milestone https://github.com/tonobo/hcloud-ruby/milestone/1