Initial Vue SFC unit test patterns

[kamorel]

Description

Adds a few small SFC tests to show how to correctly mount components with proper plugins and initial store states, access various parts of the DOM, and router mocking and testing.

Types of changes

New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING doc
• I have checked that unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

[github-actions]

Coverage Report (Application)

Totals
Statements:	75% ( 51 / 68 )
Methods:	62.5% ( 5 / 8 )
Lines:	82.61% ( 38 / 46 )
Branches:	57.14% ( 8 / 14 )

[github-actions]

Coverage Report (Frontend)

Totals
Statements:	42.81% ( 426 / 995 )
Methods:	42.31% ( 99 / 234 )
Lines:	50.59% ( 298 / 589 )
Branches:	16.86% ( 29 / 172 )

[jujaga]

From what I can gather I think this looks good. Please do one pass through to make sure that the it callback body functions do not have async on them unless they're absolutely needed; most of them do not have an explicit await statement in them, leading me to believe that most of these can be declared synchronously instead. Tentatively approving. 👍