Database semantic conventions for product-catalog service

[zhengkezhou1]

Feature Request

Is your feature request related to a problem?

I don't see any database-related content in the current repository. However, relational and non-relational databases are widely used in the real world, and almost no one in a production environment would go without them. We should provide some examples for those who want to use OpenTelemetry with databases.

Describe the solution you'd like:

product-catalog service is a good start, we can provide corresponding examples of Spans, Metrics (MySQL, PostgreSQL)

Additional Context

Feel free to add any other context about the feature request here.