Support variable expansion in .env: "VAR1=${VAR2:-default}"

[andreafalzetti]

Proposed changes

Fixes DEV-279

Currently, the .env does not support default values for variables. The library go-dotenv doesn't support the notation VAR="${VAR:-default}". (see joho/godotenv#211).

With this change the Okteto CLI will be able to expand the vars in the .env adding support for such scenario.

How to validate

1. Using latest stable test
2. Using the following manifest:

deploy:
  - env

1. Using the following .env file:

ANDREA="${ANDREA_DEFAULT:-foo}"
KEY='this is
a multiline
variable'
TEST=true

1. Run okteto deploy
2. Observe how TEST and KEY are populated correctly, while ANDREA is :-foo}

Repeat the steps with the changes and observe how all vars work as expected, by default you should get ANDREA=foo. If you run ANDREA_DEAULT=testvalue okd deploy observe the value ANDREA=testvalue in the output.

CLI Quality Reminders 🔧

For both authors and reviewers:

• Scrutinize for potential regressions
• Ensure key automated tests are in place
• Build the CLI and test using the validation steps
• Assess Developer Experience impact (log messages, performances, etc)
• If too broad, consider breaking into smaller PRs
• Adhere to our code style and code review guidelines