[Merton][WW] Allow transfer of ggw subscription

[MorayMySoc]

When a Green Garden Waste subscriber in Merton moves to another address in Merton, they can transfer the remainder of their ggw subscription to the new address

1. As long as the new address does not already have a sub
2. As long as there is a ggw on their previous property, and it is not in the renewal period
3. They have brought their bin(s) with them

This is a staff only feature.

https://github.com/mysociety/societyworks/issues/4551

[skip changelog]

[codecov]

Codecov Report

Attention: Patch coverage is 97.26027% with 2 lines in your changes missing coverage. Please review.

Project coverage is 82.86%. Comparing base (7296c20) to head (3ca0dd3).
Report is 18 commits behind head on master.

Files with missing lines	Patch %	Lines
perllib/FixMyStreet/App/Controller/Waste.pm	95.34%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5232      +/-   ##
==========================================
+ Coverage   82.36%   82.86%   +0.49%     
==========================================
  Files         409      410       +1     
  Lines       31999    33846    +1847     
  Branches     5095     5506     +411     
==========================================
+ Hits        26356    28045    +1689     
- Misses       4136     4251     +115     
- Partials     1507     1550      +43     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[dracos]

This is looking good :) I don't think any of my comments are major, and I think the end date should hook up fine for the new sub.

[dracos]

Great, think you've covered everything I asked - just a couple of knock-on things from that.

[dracos]

Almost, but... the childdata might be a hash or an array, I'm afraid! See the double loop for the same type of data at https://github.com/mysociety/fixmystreet/blob/master/perllib/FixMyStreet/Roles/Cobrand/Echo.pm#L415