[Bromley] Include notes in updates from Echo

[dracos]

And fix issue with being redirected from Echo to Bromley more than once.
Fixes https://github.com/mysociety/societyworks/issues/4633 [skip changelog]

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 82.37%. Comparing base (eeed092) to head (65a3a6f).
Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
perllib/FixMyStreet/Cobrand/Bromley.pm	87.50%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5277      +/-   ##
==========================================
+ Coverage   82.35%   82.37%   +0.01%     
==========================================
  Files         413      413              
  Lines       32668    32673       +5     
  Branches     5236     5236              
==========================================
+ Hits        26904    26914      +10     
+ Misses       4215     4211       -4     
+ Partials     1549     1548       -1     

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[nephila-nacrea]

Looks alright to me as far as I can tell. I'm just not very clear on the journey of a report being referred to Bromley from Echo or vice versa.

[nephila-nacrea]

I don't know if it would be good to have a comment or constant to explain what code 1252 refers to exactly.

[dracos]

Yeah, this could certainly do with more description (and on the wiki too, now the project's live). Hopefully the "redirecting of reports between backends" tests in t/cobrand/bromley.t at least show the behaviour of things bouncing back and forth.
(Basically, if a report is sent to Echo, they can refer it to Bromley by sending a '1252' update code to us)