Fetch currency codes from datahub

[Bjwebb]

closes #554

Remaining TODOs:

• Update the enum in the release schema

[Bjwebb]

This pull request adds withdrawn codes to the codelist.

Some active codes are renamed slightly.

The following codes have been withdrawn:

BYR,Belarussian Ruble,
EEK,Kroon,
LTL,Lithuanian Litas,
LVL,Latvian Lats,
USS,US Dollar (Same day),
ZMK,Zambian Kwacha,

The following new active codes have been added:

BYN,Belarusian Ruble,
CHE,WIR Euro,
CHW,WIR Franc,
XAG,Silver,
XAU,Gold,
XBA,Bond Markets Unit European Composite Unit (EURCO),
XBB,Bond Markets Unit European Monetary Unit (E.M.U.-6),
XBC,Bond Markets Unit European Unit of Account 9 (E.U.A.-9),
XBD,Bond Markets Unit European Unit of Account 17 (E.U.A.-17),
XPD,Palladium,
XPT,Platinum,
XSU,Sucre,
XTS,Codes specifically reserved for testing purposes,
XUA,ADB Unit of Account,
XXX,The codes assigned for transactions where no currency is involved,
ZMW,Zambian Kwacha,

There is currently one removal - XBT (Bitcoin) - as this is not in the upstream codelist.

[timgdavies]

We discussed earlier that this needs a patch version update to be merged.

We will look for any other issues in need of patch updates, and try and roll those things together over the next week - and alert the community list in case anyone happens to be relying on XBT etc.

[Bjwebb]

Some context on XBT: We think we should be able to remove this as a bugfix, as it's not in ISO4217, so therefore erroneously on our list. Our codelist docs say:

The currency for each amount should always be specified using the uppercase 3-letter currency code from ISO4217.

[jpmckinney]

I made a few edits directly.

1. Primarily, I pull directly from ISO. OK's project has no assurance of being maintained, and pulling from ISO is simple. (OK's project was already out-of-date.)
2. Use ISO8601 for validity dates.
3. Use CRLF line endings like our other CSV files.
4. Use 'Valid Until' instead of 'Withdrawal Date'. I'm not picky about this one, but I figure 'Valid Until' may be a reusable column header in future CSVs as it is more generic, whereas 'Withdrawal Date' implies an actor actively withdrawing a code, which may be less generic.

[jpmckinney]

Note that we lost another code: CNX,Peoples Bank Dollar,1989-12 (Actually, it's only lost between the commits in this PR. CNX wasn't in the old codelist.)

The explanation is in amendment 163 (docx): "The People’s Bank of China confirmed that the currency “Peoples Bank Dollar” (CNX) never existed in China (amendment no. 27)."

[jpmckinney]

ISO4217 is updated at least once a year. Here are amendment dates in the last decade:

• 2017-06-09
• 2016-02-24
• 2015-12-18
• 2015-06-19
• 2014-08-15
• 2014-03-28
• 2013-11-05
• 2013-07-23
• 2013-04-11
• 2012-08-31
• 2012-01-12
• 2011-08-31
• 2011-04-07
• 2010-12-30
• 2010-09-10
• 2010-08-17
• 2010-04-08
• 2009-05-01
• 2009-03-20
• 2009-02-06
• 2009-01-08
• 2008-10-27
• 2008-07-31

There may be implications for the version upgrade schedule (TBD) of the standard.

[jpmckinney]

Should we run this script in build_docs.sh?

[Bjwebb]

No, because that makes the build less reproducible.
We don't include other scripts that make changes that need to be committed, e.g. make_validation_schema.py

[jpmckinney]

👍 In that case, I'll create an issue to add this step to the handbook.

[jpmckinney]

Approving, but I forget the implications of merging a change to the schema in terms of governance, so I'll let @timgdavies merge.

[jpmckinney]

Also, I don't know at what point we update the changelog, but we could have something like:

#554 Update currency codelist for ISO4217 amendment 163 (2017-06-09). Note: XBT (Bitcoin) is removed from the codelist as it is not part of ISO4217.

Now that I think of it – is it more appropriate to deprecate XBT from a governance perspective? I don't think anyone was using it, though.

[timgdavies]

I've added the changelog to this branch, based on this change as giving us 1.1.2 and ready to merge into 1.1-dev.