Add lambda tests

[GiorgosNik]

Issue

ISSUE > Unit Tests for Lambdas
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Description

Add Unit Test for Lambdas under lifewatch_batch_platform\terraform\backend_lambdas\tests
Add a pipeline to run them on Push or PR that modifies the Lambdas or the pipeline: lambda-unit-tests
Also modified the behaviour of the pipelines. Now they only run on PRs and merges to main, and new commits in rapid succession cancel them (except the E2E).
E2E should now run consistently on merges to main.

Type of change

• Bug fix
• New feature
• Refactor / cleanup
• Documentation update
• Configuration / infrastructure change
• Other:

How has this been tested?

• Unit tests
• Manual testing
• No testing required

Notes for reviewers

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Checklist

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• I filled in the releated issue link
• My PR has the name of the branch
• My code follows the project's coding style
• I have reviewed my own changes before requesting review
• I have added or updated relevant documentation
• My changes do not introduce new warnings or errors
• I have not committed any secrets, credentials, or sensitive values

Related issues

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Closes #

[Kayle-Verhiel]

looks good 👍