Add x-onyxia instruction: `oneAmong`

[garronej]

The idea is to let chart authors say "this must be filled up with one object among a given array of the XOnyxia context".

- relativePath: ide/s3-single.json
  content: |
    {
      "$schema": "http://json-schema.org/draft-07/schema#",
      "type": "object",
      "properties": {
        "profileName": {
          "type": "string",
          "x-onyxia": {
            "overwriteDefaultWith": "{{profileName}}"
          }
        },
        "accessKeyId": {
          "type": "string",
          "x-onyxia": {
            "overwriteDefaultWith": "{{AWS_ACCESS_KEY_ID}}"
          }
        },
        "secretAccessKey": {
          "type": "string",
          "x-onyxia": {
            "overwriteDefaultWith": "{{AWS_SECRET_ACCESS_KEY}}"
          }
        }
      },
      "x-onyxia": {
        "oneAmong": {
            options: "{{s3_array}}",
            defaultOption: "index===0"
            // OR defaultOption: "{{profileName}}==='default'"
           //  OR defaultOption: null
      }
    }

XOnyxia

{
    // ...
    "s3_array": [
        {
            "profileName": "default",
            "AWS_ACCESS_KEY_ID": "aaa",
            "AWS_SECRET_ACCESS_KEY": "bbb"
        },
        {
            "profileName": "myprofile",
            "AWS_ACCESS_KEY_ID": "ccc",
            "AWS_SECRET_ACCESS_KEY": "ddd"
        }
    ]
}