Allow overriding label for values

[JeffersonBledsoe]

This PR introduces the concept of a 'display value' to change how a value will appear in an email or on a form. For example, a 'Single choice' field could have submitted values of ['A', 'B', 'C'], but are shown to the user as ['Option A', 'Value B', 'Option C'].

Mostly tested in production with the 'Yes/ No widget' in volto-form-block, but should work for other fields too!

Requires https://github.com/collective/volto-form-block/pull/85 for frontend

[coveralls]

Pull Request Test Coverage Report for Build 7920161992

Details

• 0 of 93 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+3.5%) to 93.205%

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Totals
Change from base Build 7919988301:	3.5%
Covered Lines:	727
Relevant Lines:	780

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💛 - Coveralls

[JeffersonBledsoe]

While getting this up-to-date, I noticed we are now removing fields who's IDs don't exist on the form block definition (great!). This logic needs updating to account for custom_field_id being sent rather than the original field ID

[folix-01]

@JeffersonBledsoe Add some tests please

[folix-01]

@JeffersonBledsoe Add some tests please

Ah ok, exists already, just opened old version of this pr in some way :D

[JeffersonBledsoe]

@JeffersonBledsoe Add some tests please

Ah ok, exists already, just opened old version of this pr in some way :D

Haha, thanks for checking! 😄 I look forward to the feedback!