Use the new microgrid API release v0.15.1

[leandro-lucarella-frequenz]

What's needed?

We need to make the SDK use the microgrid v0.14.0 as the microgrid service will be soon upgraded to this version.

Proposed solution

Bump the dependency and fix the code.

Additional context

• After this other new features present in v0.14.0 will need to be implemented, so more issues about this might come in the near future.