Add sum connector to our demos

[billg-splunk]

Is your feature request related to a problem? Please describe.
The sum connector can use span tags to create metrics. Let's incorporate into the demo.

Describe the solution you'd like
Applying sum connector into a demo flow. The examples in the blog show for instance total discount, and order totals. Both relevant metrics in the story of running a webshop (online boutique).

Describe alternatives you've considered
NA.

Additional context
https://www.splunk.com/en_us/blog/observability/opentelemetry-sum-connector.html

[billg-splunk]

Requestor: @technimad

[greatestusername-splunk]

👍