[Improvement] Enhance resolving of the same resource parameters defined in multiple "deployment_resources"

[MykhailoKashchavtsev]

Some AWS resources, like API Gateway, can be described in a number of "deployment_resources" files. In such cases there can be an issue of conflicting configuration between different files.

For example, API Gateway has the "minimum_compression_size" parameter. If this parameter is not configured in the root "deployment_resources" file and the user did a configuration mistake by specifying different values in two or more additional "deployment_resources" files, then the user cannot be sure what will the "minimum_compression_size" value be.

To avoid confusion if this happens, Syndicate should at least notify the user of the misconfiguration between different "deployment_resources". Furthermore, the process of resolving the same resource parameter when it is defined in several "deployment_resources" should be clearly described in documentation.