Create a CMake macro for defining aliases for configuration parameters

[yourslab]

This change allows aliases to be defined for macros by defining a macro called set_alias.

This is done to fix issue #1583, allowing THING_NAME to be an alias for CLIENT_IDENTIFIER.

It also fixes issue #1584 so that the values of any parameters or the file from which they are retrieved are logged. Here's an example of the log output:

Using values in test_config.h to define the following macros for http_system_test:
ROOT_CA_CERT_PATH
SERVER_HOST
HTTPS_PORT
Found the following definitions for http_system_test: ROOT_CA_CERT_PATH, SERVER_HOST, HTTPS_PORT
All required definitions for http_system_test were found - Adding to default target.

Using values in test_config.h to define the following macros for mqtt_system_test:
BROKER_PORT
Using the passed CMake arguments to define the following macros for mqtt_system_test:
CLIENT_IDENTIFIER = three
BROKER_ENDPOINT = foo
Found the following definitions for mqtt_system_test: CLIENT_IDENTIFIER, BROKER_ENDPOINT, BROKER_PORT
WARNING: mqtt_system_test missing definitions for macros: ROOT_CA_CERT_PATH, CLIENT_CERT_PATH, CLIENT_PRIVATE_KEY_PATH
To run mqtt_system_test, define required macros in mqtt_system_test/demo_config.h.

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

[aggarw13]

As part of best practices for connection with IoT Core, the Client ID should be the same as the Thing Name.
So, should we make the CLIENT_IDENTIFIER as the required config but THING_NAME as the optional config?

[yourslab]

Required in the context of this function means that a definition is required for it to compile without error. In that case, I think both of these macros should be required. In fact, nothing in the defender demo should be optional.

I've updated the docstring of set_macro_definitions to specify this.

[muneebahmed10]

The demo_config.h for Shadow defines both a client identifier:

aws-iot-device-sdk-embedded-C/demos/shadow/shadow_demo_main/demo_config.h

Line 127 in 31d6147

#define CLIENT_IDENTIFIER "testclient"

and a thing name:

aws-iot-device-sdk-embedded-C/demos/shadow/shadow_demo_main/demo_config.h

Line 169 in 31d6147

#define THING_NAME "testShadow"

Do these need to be changed?

[yourslab]

Perhaps, it would be best practice to set CLIENT_IDENTIFIER to THING_NAME in the config. The CMake only makes it so that it does that when passed as a CLI argument.