Integrate Package Dotenv

[c3bryant]

Time Tracking: MA-95

Working branch: dotenv_issue_2021

This is done when:

• Flutter dotenv package integrated
• CI/CD dotenv-ios-test, dotenv-android-test pipelines created and updated
• CI/CD test pipeline build success
• Flutter dotenv campus mobile config - secure storage

• Testing PASS on IOS (CI/CD pipeline: dotenv-ios-test)
• Testing PASS on Android (CI/CD pipeline: dotenv-android-test)

• Dotenv implementation reviewed & approved

• Documentation updated on Collab (Campus Mobile + CI/CD)
• Update CI/CD experimental pipelines with dotenv configuration
• Dotenv PR merged to experimental
• Flutter dotenv campus mobile config - team distribution

[morebytes]

Awaiting review by @alexhwu before PR can be made