[v2] Add configuration to disable host prefix injection

[kdaily]

Issue #, if available:

Description of changes:

This change deviates from the upstream botocore to add the ability to disable jost prefix injection. It changes the default for inject_host_prefix in the Config object to be None (from True) so that the value can be determined using the configuration precedence. The fallback if the value remains True if it is set to None to preserve the CLI default behavior.

Testing

Tested with the following commands which uses an operation-specific host prefix:

1. Default case (no disable host prefix configuration set) results in the host prefix being added:

$ aws omics create-sequence-store --name "test-sequence-store1" --description "Test store" --endpoint-url https://localhost:1234/ --tags "Environment=Test"

Could not connect to the endpoint URL: "https://control-storage-localhost:1234/sequencestore"

2. Set config environment variable to False, which is the same as the default behavior:

AWS_DISABLE_HOST_PREFIX_INJECTION=False aws omics create-sequence-store --name "test-sequence-store1" --description "Test store" --endpoint-url https://localhost:1234/ --tags "Environment=Test"

Could not connect to the endpoint URL: "https://control-storage-localhost:1234/sequencestore"

3. Set config environment variable to True, which prevents the host prefix from being prepended to the endpoint URL:

$ AWS_DISABLE_HOST_PREFIX_INJECTION=True aws omics create-sequence-store --name "test-sequence-store1" --description "Test store" --endpoint-url https://localhost:1234/ --tags "Environment=Test"

Could not connect to the endpoint URL: "https://localhost:1234/sequencestore"

I also confirmed the behavior applies when using the configuration file setting disable_host_prefix_injection, and even when not using a custom endpoint URL.

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[hssyoo]

Looks good, just a couple small suggestions. I'm also curious if there are existing unit/functional tests where you can actually set the environment variable or create a config file to test that they resolve correctly E2E.

[hssyoo]

I think we should leave this in here and when we compute the value, we can check if this is not None.

[kdaily]

Sure, not opposed to this. I went for self-containing all of the logic in the compute method.

[hssyoo]

So here we can remove client_config as a parameter and check

if config_kwargs.get('inject_host_prefix') is not None:
    # User explicitly set a client config value. Respect it and return.
    return

[ashovlin]

Could we wait to merge until we figure out the plan for botocore? Want to understand where V1 vs. V2 will land.

[ashovlin]

Could we document the specific environment variable and setting name here?

Suggested change

	"description": "Configure if the host prefix is prepended to the request URL in the shared configuration file or via an environment variable"
	"description": "Allow disabling the prepending of the host prefix to the request URL via ``disable_host_prefix_injection`` in the shared configuration file or the ``AWS_DISABLE_HOST_PREFIX_INJECTION`` environment variable"