Support for custom terraform cli builds

[alfespa17]

Terrakube will support terraform cli custom builds or custom cli mirrors, the only requirement is to expose an endpoint with the following structure

Example Endpoint: https://eov1ys4sxa1bfy9.m.pipedream.net/

{
   "name":"terraform",
   "versions":{
      "1.3.9":{
         "builds":[
            {
               "arch":"amd64",
               "filename":"terraform_1.3.9_linux_amd64.zip",
               "name":"terraform",
               "os":"linux",
               "url":"https://releases.hashicorp.com/terraform/1.3.9/terraform_1.3.9_linux_amd64.zip",
               "version":"1.3.9"
            }
         ],
         "name":"terraform",
         "shasums":"terraform_1.3.9_SHA256SUMS",
         "shasums_signature":"terraform_1.3.9_SHA256SUMS.sig",
         "shasums_signatures":[
            "terraform_1.3.9_SHA256SUMS.72D7468F.sig",
            "terraform_1.3.9_SHA256SUMS.sig"
         ],
         "version":"1.3.9"
      }
   }
}

The API and Executor component will use the environment variable CustomTerraformReleasesUrl to load the terraform CLI builds information, by default it will use https://releases.hashicorp.com/terraform/index.json

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

15.4% Coverage
0.0% Duplication

[alfespa17]

AzBuilder/terrakube-helm-chart#46