Support user-defined metric formulas

[cwasicki]

What's needed?

Support for the RPC functions to request aggregated metrics based on user-defined formulas should be added. This encompasses functions for historical data and streaming.

Proposed solution

No response

Use cases

No response

Alternatives and workarounds

No response

Additional context

No response

[cwasicki]

Not v1.0

[flora-hofmann-frequenz]

I think with recent developments this is back on for v1.0.0 again, right @cwasicki ?

[cwasicki]

I think with recent developments this is back on for v1.0.0 again, right @cwasicki ?

Agree.