fix: [DevOps] Fix failing e2e script

[Jonas-Isr]

Context

Our e2e script was failing before the actual tests were run (see example run).

• The main issue seemed to be that the evaluated secret had special characters inside that were interpreted as parts of a shell command. To fix this, I now use ' instead of " when reading the secrets.
• Also, no Slack notification was sent after the runs failed. This was due to the Slack GH-action failing if one of the blocks of a multi-block message is empty (see reference). To fix this, I added a whitespace to the second block (that otherwise would be empty if the script fails for a reason that is not a test-failure).

Link to successful run of e2e tests on this branch (without running the one test that is actually failing right now, will fix that in a separate PR).

Feature scope:

• fix reading secrets
• fix sending Slack notification

Definition of Done

• Functionality scope stated & covered
• Tests cover the scope above
• Error handling created / updated & covered by the tests above
• Aligned changes with the JavaScript SDK
• Documentation updated
• Release notes updated