[SIGMON-309] signal_metadata used

Context

• task: https://its.cern.ch/jira/browse/SIGMON-309
• lhc-sm-api MR: lhc-sm-api!142 (merged)

What was done

• signal_metadata used instead of SignalMetadata
• timestamp parameter passed to the signal_metadata's methods (if possible)

TODO

• ?

QA

• no sonar:
• notebooks executed:

Review objectives

• assessment of code functionality
• assessment of code quality
• identifying potential refactorings / logic common to other projects
• knowledge sharing
• getting help to understand a piece of code