[Feature] Warn limit number of countries in TE request

[hjoaquim]

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

   • Allowing more than N countries in a TE request would break with a http code of 400.

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

   • If countries are above 28 (which is the number when it usually starts to fail), adds a warning and an extra info message when it fails.

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

   • Low - small improvement on UX.

4. Testing Done:

   • Experiment with any amount of countries from openbb_platform/providers/tradingeconomics/openbb_tradingeconomics/utils/countries.py:

from openbb import obb
countries = [...]
obb.economy.calendar(provider="tradingeconomics", country=countries).to_df()

5. Reviewer Notes (optional):

   • It looks like it depends on the countries we're sending. Sometimes it fails for 28, other times 31/32. I wasn't able to get more than 32 with any combination of countries. Also, couldn't find any information related with this limit on TE API docs.
   • Limiting to the number of characters doesn't work as well, usually starts failing when url is arround len 400.
   • See also discussion on [Feature] Limit number of countries in TE request #6301
   • cc @andrewkenreich