Make use of logback's MDC to add context to log statements

[nscuro]

Current Behavior

Dependency-Track performs many tasks asynchronously. Status updates, warnings, and errors are logged during task execution, however those logs lack context:

• When BOM processing fails, it's unclear for which BOM, uploaded to what project
• When VEX processing fails, it's unclear for which VEX, uploaded to what project
• When repository metadata analysis fails, it's unclear for which component, and for what repository
• etc.

Proposed Behavior

Logback offers a feature to add additional context to log statements via Mapped Diagnostic Context (MDC).

We should use that to attach context information, for example:

• Project UUID, name, version
• Component UUID, name, version
• BOM / VEX format, spec version, serial number, version
• etc.

wherever appropriate. When logging to JSON format, those context variables are represented as dedicated JSON fields and can thus be indexed by log aggregators (Elasticsearch, Splunk, ...).

Checklist

• I have read and understand the contributing guidelines
• I have checked the existing issues for whether this enhancement was already requested