fix: add Referer to Dapp Viewed events

[NicolasMassart]

Description

• add Referrer to Dapp Viewed events
• update unit test
• fix unit test names according to guidelines for consistency with new test

Related issues

Fixes https://github.com/MetaMask/mobile-planning/issues/1601

Manual testing steps

Feature: Send Dapp Viewed with Referrer

  Scenario: Open dapp from in app browser
    Given the app is installed and setup
    And user goes into in app browser
    And user loads a dapp (must be a dapp you can connect with your wallet like https://portfolio.metamask.io/)
  
    When user connects dapp to Metamask
    And approves connection
  
    Then `Dapp Viewed` event is sent to Mixpanel
    And has `Referrer` property filled with the domain scheme+name, example https://portfolio.metamask.io/

  Scenario: Open dapp from external browser
    Given the app is installed and setup
    And user goes into external browser
    And user loads a dapp (must be a dapp you can connect with your wallet like https://portfolio.metamask.io/)
  
    When user connects dapp to Metamask using WalletConnect
    And approves connection
  
    Then `Dapp Viewed` event is sent to Mixpanel
    And has `Referrer` property filled with the domain scheme+name, example https://portfolio.metamask.io/

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I’ve followed MetaMask Coding Standards.
• I've clearly explained what problem this PR is solving and how it is solved.
• I've linked related issues
• I've included manual testing steps
• I've included screenshots/recordings if applicable
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.
• I’ve properly set the pull request status:
  • In case it's not yet "ready for review", I've set it to "draft".
  • In case it's "ready for review", I've changed it from "draft" to "non-draft".

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[github-actions]

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 43.75%. Comparing base (9739816) to head (9e11f8b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8991   +/-   ##
=======================================
  Coverage   43.75%   43.75%           
=======================================
  Files        1273     1273           
  Lines       31113    31113           
  Branches     3165     3165           
=======================================
  Hits        13612    13612           
  Misses      16688    16688           
  Partials      813      813           

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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[MarioAslau]

Looks great @NicolasMassart ! Thank you for the context

[Cal-L]

Let's wait for @gauthierpetetin to confirm

[Cal-L]

LGTM