13309 Add ability to clear LU form dropdowns

[godfreyyeung]

Summary

Allows users to clear the dropdown selection on the Land Use Form Page. Including for these questions:

1 PAS/RWCDS/Land Use Form > applicant geographic state
2 Land Use Form > Zoning Map Amendments section > Total Area of All Zoning Lots
3 Land Use Form > Zoning Map Amendments section > Existing Zoning District
4. Land Use Form > Environmental Review section > Lead Agency
5. Land Use Form > Proposed Actions section > Previously Approved Action code
6. Land Use Form > Proposed Actions section > Zoning Resolution action is Pursuant to

Task/Bug Number

Fixes AB#13309

Technical Explanation

• For questions 1-3 above, the solution was simply to set the @allowClear={{true}} argument on the Power Selects. This enables a Power Select built-in feature where a user can click an "x" to assign the bound property a null value. This worked because those properties are simple text or integer values.

• For questions 4-6 above, the solution was more complex because they deal with models/objects. Also, the power selects in 4-5 read the options from one model and assign the selected option to another ("target") model. They currently do so by assigning the selected option's ID to an auxiliary, made-up "*chosenId" field on the target model, and relying on the backend to read that chosenId and patch relationships accordingly. Thus, this PR follows that example, and modifies the backend to delete relationships according to the incoming value of the "*chosenId" fields.

This whole workflow should be reworked in the future. Ideally, these powerselects read and write to the same model, or polymorphic models. The frontend should associate and disassociate models based on the dropdown selections, so that when the form is saved, the proper JSONAPI compliant requests are generated.

• Sets up a new disassociateHasOne() method on the CRM Service for disconnecting an 1:1 entity relationship

• Patches up a few Power Select components so that the concerned property is displayed as the selected value on load. Previously they displayed the value as the placeholder, so it would appear gray instead of black.

• Another future todo: Questions 1-3 and 4-6 have different styles for the "clear" button. One is a black "x", the other is the text "clear". we should design a consistent style for all dropdowns.

[codecov]

Codecov Report

Merging #866 (c4573c5) into develop (2308c29) will decrease coverage by 1.03%.
The diff coverage is 61.53%.

@@             Coverage Diff             @@
##           develop     #866      +/-   ##
===========================================
- Coverage    85.66%   84.63%   -1.04%     
===========================================
  Files          114      113       -1     
  Lines          900      911      +11     
===========================================
  Hits           771      771              
- Misses         129      140      +11     

Impacted Files	Coverage Δ
...ackages/landuse-form/zoning-resolution-dropdown.js	50.00% <50.00%> (-25.00%)	⬇️
...ts/packages/landuse-form/proposed-action-editor.js	68.42% <60.00%> (-11.58%)	⬇️
...pp/components/packages/landuse-form/lead-agency.js	69.23% <75.00%> (-19.66%)	⬇️
client/app/components/project/package-section.js	6.66% <0.00%> (-13.34%)	⬇️
client/app/models/package.js	95.34% <0.00%> (ø)
client/app/helpers/to-locale-string.js

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[trbmcginnis]

Awesome! Your PR description is so thorough and amazing, I love it.

I left some comments for just removing some code that was rendered obsolete by your changes (just a little bit of clean-up, nothing major), but other than that it looks great, thanks!

[allthesignals]

Looks good, thank you!! Just left a few questions.