Publisher header consistency

[Lukewh]

Done

Ensured the headers for all publisher pages are consistent

• Added some extra data to certain pages and views
• Updated navigation.js to set the users displayname in session storage
• Updated PageHeader component to conditionally show "By [publishername]" based on the session storage display name

How to QA

• Visit a snap you own, go through the publisher pages
  • Make sure the header shows the snap title, not the snap name
• Visit a snap you don't own, go through each publisher page
  • Make sure the header shows the snap title and "by [publishername]"

Issue / Card

Fixes https://warthogs.atlassian.net/browse/WD-7927

Screenshots

[webteam-app]

Demo starting at https://snapcraft-io-4485.demos.haus

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (615acb6) 79.79% compared to head (a04b70f) 79.79%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4485   +/-   ##
=======================================
  Coverage   79.79%   79.79%           
=======================================
  Files         207      207           
  Lines       10472    10474    +2     
  Branches      924      926    +2     
=======================================
+ Hits         8356     8358    +2     
  Misses       1992     1992           
  Partials      124      124           

Flag	Coverage Δ
javascript	68.43% <100.00%> (+0.01%)	⬆️
python	85.70% <ø> (ø)

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[codeEmpress1]

LGTM