Stop slashes breaking csv report downloads

[MorayMySoc]

Removes slashes from category names used in file name for csv download.

Backward slash makes the file not retrievable.
Forward slash makes the file not saveable.

https://github.com/mysociety/societyworks/issues/2679

[codecov]

Codecov Report

Merging #3642 (010af6a) into master (1711f9a) will decrease coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3642      +/-   ##
==========================================
- Coverage   82.69%   82.64%   -0.06%     
==========================================
  Files         348      348              
  Lines       23750    23750              
  Branches     3609     3609              
==========================================
- Hits        19641    19629      -12     
- Misses       2973     2984      +11     
- Partials     1136     1137       +1     

Impacted Files	Coverage Δ
perllib/FixMyStreet/Reporting.pm	94.96% <ø> (ø)
perllib/FixMyStreet/Cobrand/Bromley.pm	92.60% <100.00%> (ø)
web/js/front.js	82.25% <0.00%> (-1.62%)	⬇️
web/cobrands/fixmystreet/assets.js	88.23% <0.00%> (-1.52%)	⬇️
perllib/Utils.pm	97.97% <0.00%> (-1.02%)	⬇️
web/cobrands/fixmystreet-uk-councils/alloy.js	90.09% <0.00%> (-1.00%)	⬇️

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[chrismytton]

In terms of testing you probably want something similar to the existing "export as CSV" test but using a category with a slash in the name.

fixmystreet/t/app/controller/dashboard.t

Lines 182 to 224 in 76436d0

	subtest 'export as csv' => sub {
	$mech->create_problems_for_body(1, $body->id, 'Title', {
	detail => "this report\nis split across\nseveral lines",
	category => 'Problem one',
	areas => ",$alt_area_id,2651,",
	});
	$mech->get_ok('/dashboard?export=1');
	my @rows = $mech->content_as_csv;
	is scalar @rows, 19, '1 (header) + 18 (reports) = 19 lines';
	is scalar @{$rows[0]}, 22, '22 columns present';
	is_deeply $rows[0],
	[
	'Report ID',
	'Title',
	'Detail',
	'User Name',
	'Category',
	'Subcategory',
	'Created',
	'Confirmed',
	'Acknowledged',
	'Fixed',
	'Closed',
	'Status',
	'Latitude',
	'Longitude',
	'Query',
	'Ward',
	'Easting',
	'Northing',
	'Report URL',
	'Device Type',
	'Site Used',
	'Reported As',
	],
	'Column headers look correct';
	is $rows[5]->[15], 'Trowbridge', 'Ward column is name not ID';
	is $rows[5]->[16], '529025', 'Correct Easting conversion';
	is $rows[5]->[17], '179716', 'Correct Northing conversion';
	};

[chrismytton]

⚔️