Add backend changes for missing hosts

[chris1984]

• Added route
• Added GET controller method for API
• Added new controller for UI with GET route
• Added permissions for routes
• Updated model with validations
• Fix model file name
• Fix migration (was not adding the organization_id column for some reason, this way it does)

Getting data back on get method :)

19:21:52 rails.1   | 2023-05-19T19:21:52 [I|app|9d49580f] Started GET "/api/v2/organizations/3/rh_cloud/missing_hosts" for 192.168.196.1 at 2023-05-19 19:21:52 -0400
19:21:52 rails.1   | 2023-05-19T19:21:52 [I|app|9d49580f] Processing by Api::V2::RhCloud::InventoryController#get_hosts as JSON
19:21:52 rails.1   | 2023-05-19T19:21:52 [I|app|9d49580f]   Parameters: {"apiv"=>"v2", "organization_id"=>"3"}
19:21:52 rails.1   | 2023-05-19T19:21:52 [D|app|9d49580f] Body: {"id":1,"name":"foo.example.com","organization_id":3,"insights_id":"111-222","rhsm_id":"111-222","ip_address":"192.168.196.1"}

[chris1984]

@ShimShtein updated, want me to start working on tests for the get/index controller methods or do you have something else in mind for the next steps?

[chris1984]

@ShimShtein Added the POST methods and got the permissions fixed up, let me know how this looks. I am sure it looks like 💩 🙃

[chris1984]

Looks quite good actually. A couple of smaller comments and we're there.

@shim Thanks 😃 also removed the rescue from the POST in the inventory controller as well. Marked it ready for review and removed it out of DRAFT status.

[ShimShtein]

@chris1984 , could you please rebase this one?

[chris1984]

@ShimShtein updated :)

[chris1984]

@ShimShtein can this get a merge?