[BUG] Backward-incompatible ARCANE_CONNECTIONSTRING secret

[s-vitaliy]

Description

The secret that contains arcane connection string should have a key named ARCANE__CONNECTIONSTRING (two underscores instead of one) for backward compatibility with old CRD layout.

Steps to reproduce the issue

1. Create a K8S secret that does not contain ARCANE__CONNECTIONSTRING key
2. Start a stream with this secret
3. The stream runner fails

Describe the results you expected

The stream runner should be able to read old secrets format until SneaksAndData/arcane-operator#91 is implemented

System information

v.0.0.4, only related to a stream runner

[s-vitaliy]

Resolved with #37