adding continuous profiling

[spottsdd]

Description

Please, provide here a short description.

The Gemfile for the backend already uses latest version of the Ruby ddtrace library, so Continuous Profiling is supported. This configures Profiling to be enabled. In Ruby this requires adding google-protobuf, enabling in the initializer file (this can be overridden with env, and adding ddtracerb exec to the app execution command.

Checklist

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• No unintended changes are included
• Spelling is correct
• There are tests covering new/changed functionality
• Commits have meaningful names and changes. CR remarks-like commits are squashed.
• Proper labels assigned. Use WIP label to indicate that state