Prefetching users to avoid N+1 queries

[abithyzis]

Description

Prefetching users to avoid one query for each user session displayed

Motivation and Context

Refs #94

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #107 into master will increase coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #107      +/-   ##
==========================================
+ Coverage   88.92%   88.96%   +0.03%     
==========================================
  Files          10       10              
  Lines         280      281       +1     
  Branches       31       31              
==========================================
+ Hits          249      250       +1     
  Misses         23       23              
  Partials        8        8

Impacted Files	Coverage Δ
user_sessions/admin.py	100% <100%> (ø)	⬆️

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[Bouke]

Looks like a good PR. I'll merge it after the jazzband configuration has been resolved: #105 (comment).