[BugFix] Fix FMP Market Snapshots

[deeleeramone]

1. Why? (1-3 sentences or a bullet point list):

   • Inconsistent types returned by FMP result in random validation errors.

   • 0 is returned instead of None in a field of Unix timestamps.

2. What? (1-3 sentences or a bullet point list):

   • Added a bunch of validators to the FMP model to handle date parsing exceptions and clear all empty strings or NaN-like values.

   • substitute ForceInt in place of int.

   • "market" parameter made to accept lower case instead of ALL_CAPS

3. Impact (1-2 sentences or a bullet point list):

   • Improved stability and standardization.

   • Changes affect only FMP.

   • Endpoint is not currently used by Pro

   • Applied json_schema_extra = {"x-unit_measurement": "percent", "x-frontend_multiply": 100} to FMP change_percent field.

   • "price" --> "last_price"

   • "avg_volume" --> "volume_avg"

   • "timestamp" --> "last_price_timestamp"

   • "market" parameter made to accept lower case instead of ALL_CAPS

4. Testing Done:

   • Tested all choices to verify no validation errors were raised by surprise values.

Before:

OpenBBError: 1 validation error for FMPMarketSnapshots
avgVolume
  Input should be a valid integer, got a number with a fractional part [type=int_from_float, input_value=25443.3, input_type=float]

After: