Add support for consumption data retrieval (dashboard/meter endpoints)

[FlorentPoinsaut]

Context

The library currently retrieves production/energy data through playback endpoints (optimizer/string/inverter/site aggregation).
However, it does not appear to expose consumption data retrieval (load/usage), for example via endpoints such as:

• /services/dashboard/inverters/power/sites/{site_id}
• and/or other SolarEdge consumption/meter endpoints (depending on API availability)

Problem

Without consumption data, it is harder to support full energy monitoring use cases such as:

• production vs consumption tracking
• self-consumption calculations
• grid import/export analysis

Proposal

Add one or more public methods to retrieve consumption data, e.g.:

• async_get_consumption_data(...)

with:

• time granularity aligned with async_get_energy_data where possible (hour/day)
• structured output similar to existing energy models (timestamp + values + units)

Suggested implementation notes

• Identify the most stable SolarEdge endpoint(s) for consumption/meter data
• Reuse existing authentication/session flow
• Add parsing and unit normalization
• Handle HTTP errors and partial/incomplete payloads robustly
• Add unit tests with fixtures (similar to existing playback tests)

Acceptance criteria

• A public API can fetch consumption data for a site
• Returned data is timestamped and units are documented
• Tests cover URL building, parsing, and error handling
• README/docs include an example usage

Expected impact

Enable full energy monitoring (production + consumption) directly from solaredge-web.

[FlorentPoinsaut]

Thanks a lot @tronikos!!!