[ENG-4818] Use provider favicon for preprint discover page

[futa-ikeda]

• Ticket: ENG-4818
• Feature flag: n/a

Purpose

• Use provider's favicon when looking at branded preprint discover page

Summary of Changes

• Add afterModel hook to preprint-discover route to add favicon (same logic as lib/registries/addon/branded/route.ts)
  • Can move this afterModel hook to parent route once preprints landing page rewrite

Screenshot(s)

• favicon associated with a preprint-provider in admin app and used in the browser tab below
  

Side Effects

QA Notes

• Please make sure the preprint provider is using a given favicon in the admin app by going to admin.staging.osf.io/provider_asset_files/<asset_id>/

[coveralls]

Pull Request Test Coverage Report for Build 6551520933

• 0 of 3 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.05%) to 71.167%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
app/preprints/discover/route.ts	0	3	0.0%

Totals
Change from base Build 6511581413:	-0.05%
Covered Lines:	5941
Relevant Lines:	8132

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💛 - Coveralls