Fix multiday div-adjust ; Tidy adjust args

[ValueRaider]

Dividend adjustment of multi-day intervals is broken - always was - and in some cases the 'Adj Close' returned by Yahoo is wrong. Details & planned solution in Issue #1273. Most code changes are in Ticker._get_div_adjusted_multiday_prices().

Make some other changes:

Changed Ticker.history(auto_adjust=...) default to False, finally matching yf.download behaviour. Deleted back_adjust argument, it just duplicated auto_adjust.

Renamed auto_adjust -> div_adjust. auto_adjust still works but prints a "Deprecated" message, when #1423 is complete can limit prints to one time.

@RudyNL Any thoughts? #1333

[paulmcq]

Line yfinance/base.py 1470:
if "period" in hist_args and hist_args["period"] is not None:
might be more legible as:
if hist_args.get("period", None) is not None:

[ValueRaider]

@paulmcq You can review code in "Files changed" tab -> click '+' button by code

[paulmcq]

might be more legible as:
if hist_args.get("period", None) is not None:

[ricardoprins]

Here's what I got from confronting the data from #1273:

import yfinance as yf


ticker = "i3e.l"
data = yf.Ticker(ticker)
start = "2022-11-07"
end = "2022-11-14"

df_yr = data.history(start=start, end=end, interval="1d")
print(df_yr[['Close', 'Adj Close', 'Dividends']])

df_yr = data.history(start=start, end=end, interval="1wk")
print(df_yr[['Close', 'Adj Close', 'Dividends']])

Results:

NOTICE: yfinance.Ticker::history(): Be aware that dividend-adjustment is now default disabled, default used to be enabled
                               Close  Adj Close  Dividends
Date                                                      
2022-11-07 00:00:00+00:00  24.600000  23.223310     0.0000
2022-11-08 00:00:00+00:00  24.500000  23.128904     0.0000
2022-11-09 00:00:00+00:00  23.549999  22.232069     0.0000
2022-11-10 00:00:00+00:00  23.500000  22.319923     0.1425
2022-11-11 00:00:00+00:00  23.500000  22.319923     0.0000
                           Close  Adj Close  Dividends
Date                                                  
2022-11-07 00:00:00+00:00   23.5  22.184866     0.1425

Process finished with exit code 0

Just a quick note: I had to edit line 226 in base.py to make it work, matching what we have in dev:

dt_now = _pd.Timestamp.utcnow()

It seems to me that the modifications are doing what was expected of them unless I'm missing something here.

[ValueRaider]

I tagged review for discussion - should yfinance do this?

[ricardoprins]

I think it could indicate the distortion and give the user the option to enable/disable the correction via flag.

[ValueRaider]

I could link the 'dividend adjustment fix' to argument repair=True. Which is the bulk of this PR.