RUMM-110 Send single message to Datadog

[ncreated]

This PR sets up component related to logs upload. From now, it is possible to upload single log after calling:

logger.info("Test message from ios-app-example")

on the Logger component.

What's done?

It introduces simple architecture which will be later evolved. On top, there are two packages:

• Logs,
• Network.

Network contains only things related to HTTP communication, with HTTPClient being the main component.

Logs package adds SDK logic-related stuff, with Log model, LogsUploader (that uses HTTPClient) and LogsUploadRequestEncoder for request body encoding.

This architecture follows some of the logic-separation principles from Android SDK ⭐️ project.

What will come in other JIRAs?

This code is not yet covering important things decoupled to other JIRAs:

• logs persistence;
• logs batching;
• threading.

[ncreated]

The size of this PR comes mainly from the amount of mocks I had to configure for unit tests 🙄 🙌 . I will aim for keeping next PRs smaller thanks to the foundations I set up here.