Implement availability endpoint

[bakhterets]

https://github.com/orgs/opentelekomcloud-infra/projects/15/views/1?pane=issue&itemId=81582313

Goals:

1. add to openapi schema
2. implement endpoint {v1|v2}/availability (calculation and response)

[sgmv]

Details:

1. Get request to /v2/availability (we should receive availability for all components for the last 6 months)

   [
   {
   "id":158,
   "name":"Auto Scaling",
   "region": "EU-DE",
   "availability":[
         {
           "year": 2024,
           "month": 5,
           "percentage":100
         },
         {
           "year": 2024,
           "month": 6,
           "percentage":100
         },
         {
           "year": 2024,
           "month": 7,
           "percentage":100
         },
         {
           "year":2024,
           "month": 8,
           "percentage":100
         },
         {
           "year": 2024,
           "month": 9,
           "percentage":100
         },
         {
           "year": 2024,
           "month": 10,
           "percentage":99.999666
         }
   ]
   }
   ]