bug(lib): mermaid diagram bug solution

[sanketshevkar]

Closes #38

More context here: accordproject/concerto#649

Changes

• visitRelationship method from MermaidVisitor class was overriding the same method in DiagramVisitor class, which caused this issue.
• Changed visitRelationship from MermaidVisitor class to writeRelationshipAggregation method, which acts as helper method now create the relationship-aggregation line in mermaid diagram code.

Flags

• MermaidVisitor class no more has visitRelationship method, not sure if this would break the visitor pattern. Wanted to clarify if this is the correct approach.

Related Issues

• Issue Mermaid diagram is incorrect for relationships concerto#649

Author Checklist

• Ensure you provide a DCO sign-off for your commits using the --signoff option of git commit.
• Vital features and changes captured in unit and/or integration tests
• Commits messages follow AP format
• Extend the documentation, if necessary
• Merging to main from fork:branchname

[coveralls]

coverage: 98.942%. remained the same when pulling 4173fad on sanketshevkar:sanketshevkar/i38/mermaid-diagram-code-correction into c1e909f on accordproject:main.

[dselman]

Great!