[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 85.71429% with 1 line in your changes missing coverage. Please review.

Project coverage is 82.42%. Comparing base (fbbc68c) to head (856bed4).

Files with missing lines	Patch %	Lines
perllib/FixMyStreet/Cobrand/Bromley.pm	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5277   +/-   ##
=======================================
  Coverage   82.42%   82.42%           
=======================================
  Files         415      415           
  Lines       32837    32832    -5     
  Branches     5265     5265           
=======================================
- Hits        27065    27063    -2     
+ Misses       4216     4213    -3     
  Partials     1556     1556           

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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)