Support for `&` char in ticker symbols (e.g., M&M.NS)

[givek]

Hi! I'm new to open source and would like to ask for guidance before submitting a PR.

I've encountered an issue where Indian stock tickers such as M&M.NS fail to parse because the & character is not allowed.

Reference: https://finance.yahoo.com/quote/M&M.NS/

Current behavior:

$ python -m beanprice.price -e 'INR:yahoo/M&M.NS'

usage: bean-price [-h] [-e] [-v] [-d DATE] [--update] [--update-rate {daily,weekday,weekly}] [--update-compress UPDATE_COMPRESS] [-i] [-u] [-c] [-a]
                  [-s] [-w WORKERS] [-n] [--cache CACHE_FILENAME] [--no-cache] [--clear-cache]
                  sources [sources ...]
bean-price: error: Invalid source "INR:yahoo/M&M.NS". Supported format is "CCY:module/SYMBOL"

Proposed fix:

In beanprice/price.py line 167, add & to the allowed characters in the regex:

Before:

match = re.match(r"([a-zA-Z]+[a-zA-Z0-9\._]+)/(\^?)([a-zA-Z0-9:=_\-\.\(\)]+)$", source)

After:

match = re.match(r"([a-zA-Z]+[a-zA-Z0-9\._]+)/(\^?)([a-zA-Z0-9:=_\-\.\(\)&]+)$", source)

I tested this change locally, and it resolves the issue for M&M.NS.

This would require updating one test case in price_test.py (line 377), which currently expects yahoo/CNYUSD&X to be invalid.

Would the maintainers be open to accepting a PR with this change? I understand that & in ticker symbols is very uncommon, but it is required for certain international markets such as India.

Thank you!

[slashformotion]

I am not the maintainer, but this looks good to me. I'd say go ahead and send the PR.

[slashformotion]

might clash with #131 if it get merged tho

[givek]

@slashformotion I've opened the PR. Let me know if you'd like me to make any changes. Thanks!