Should we do union of configuration properties specified in `dab-config.json` and `dab-config.<Environment>.json`?

[Aniruddh25]

Currently, the configuration properties are NOT additive. So, for example, a property is defined in dab-config.json, but NOT defined in dab-config.Development.json, it will be considered undefined since we give preference to the environment specific file.

This issue is to discuss if such a union is desirable? What to do when missing properties are conflicting with each other?

See this discussion: https://github.com/Azure/data-api-builder/pull/678/files#r947322896

[seantleonard]

May need to make RuntimeConfigProvider into a Asp.net configuration provider: https://learn.microsoft.com/en-us/dotnet/core/extensions/configuration-providers#memory-configuration-provider
Such that any key value pairs created in one file can be replaced by more precedent config files that define only the changes from the base file.