Add non-composite custom money

[mathemancer]

Fixes #1094

This adds a custom money type called MATHESAR_TYPES.MATHESAR_MONEY based on underlying NUMERIC storage.

Technical details

Extra features over NUMERIC:

• a column of MATHESAR_TYPES.MATHESAR_MONEY will be reflected as such, notifying the UI that it should apply whatever display options are relevant.

• For casting from text types (TEXT, VARCHAR, CHAR(n), etc.), many inputs which wouldn't be allowed for NUMERIC are handled properly. Each of

  • '$1,000.00'
  • '1,000.00$'
  • '$1'
  • '-$1'
  • '($1)' -- common way to write negative numbers in accounting
  • '$1-' -- negative number in some locales
  • '$-1' -- some locales put the negative between the currency symbol and the number
  • '1$'
  • '$ 1'
  • '$1,000,000'
  • '$1,234,567.1234'
  • '1,000,000$'
  • '$1 000,000'
  • '1 000,000$'
  • '1.000,000$'
  • '$1.000,00 HK'
  • 'EUR 1.000,00'
  • '€1.000,00'
  • '1.000,00€'
  • '€1 000'
  • '1 000€'
  • '₿1,324.23466 BTC'
  • '₹1,00,000'
  • '1,00,000₹'
  • '₹1,00,000.00'
  • '1,00,000.00₹'
  • '10,00,000.00₹'
  • '₹10,00,00,000.00'
  • '10,00,00,000.00₹'

  is cast to the proper numeric value. Note that we allow currency symbols (non-numeric characters) at the beginning, end, or both of the numeric portion. We allow ,, ., or (space) as group separators. We allow either , or . as decimal points (but the decimal point needs to be distinct from the group separator). For grouping, we handle both the international 3-digit group system or the lakh, crore, etc. system. There are some notable things we can't allow, since we're locale-agnostic when reading text as money, or other reasons:

  • '1' -- no currency symbol
  • '$1,000' -- this would be $1 in the German locale, but $1000 in the American English locale.
  • '1$1000$1' -- we only allow one continuous substring of number data (while handling group separators and decimal points)
  • '₹10 00 00 000.00' -- only , and . are allowed for the group separator and decimal point respectively in the lakh system
  • '₹10.00.00.000,00' -- same

In any case where we handle the input, it will be translated appropriately into the DB's locale for parsing as a NUMERIC for storage.

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the master branch of the repository
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no
  visible errors.

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[codecov-commenter]

Codecov Report

Merging #1137 (1cac166) into master (8631e1c) will increase coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1137      +/-   ##
==========================================
+ Coverage   93.30%   93.39%   +0.09%     
==========================================
  Files         112      113       +1     
  Lines        4269     4332      +63     
==========================================
+ Hits         3983     4046      +63     
  Misses        286      286              

Flag	Coverage Δ
pytest-backend	93.39% <100.00%> (+0.09%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
db/columns/operations/infer_types.py	97.14% <ø> (ø)
mathesar/database/types.py	97.67% <ø> (ø)
db/types/__init__.py	100.00% <100.00%> (ø)
db/types/base.py	97.56% <100.00%> (+0.01%)	⬆️
db/types/install.py	100.00% <100.00%> (ø)
db/types/money.py	100.00% <100.00%> (ø)
db/types/multicurrency.py	100.00% <100.00%> (ø)
db/types/operations/cast.py	100.00% <100.00%> (ø)

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[silentninja]

Great work @brent!. I removed a stale print statement in line db/types/operations/cast.py:314

[silentninja]

Please remove this print statement

[mathemancer]

Thanks for catching that.