MQTT: Restore config file parser for authentication support

[kumajaya]

No description provided.

[azoitl]

Does this work also for multiple clients connections?

[kumajaya]

Yes, I've tested it. From MQTTClientConfigParser.h:

"The parser looks for an endpoint, and only after it matches the one passed as argument, it starts storing the following information, and it will keep reading after another endpoint other the end of file is found"

OPC UA should have the same behavior, I will confirm it.

[azoitl]

Yes, I've tested it. From MQTTClientConfigParser.h:

"The parser looks for an endpoint, and only after it matches the one passed as argument, it starts storing the following information, and it will keep reading after another endpoint other the end of file is found"

OPC UA should have the same behavior, I will confirm it.

Cool. If you want to update the docs they are now also on github: https://github.com/eclipse-4diac/4diac-documentation