feat(cactus-example-discounted-asset-trade): use openapi sawtooth connector

[outSH]

• Refactor discounted asset trade sample to use openapi sawtooth connector
  instead of sawtooth-socketio.
• Remove sawtooth-socketio connector since it's not used any more.

Depends on: https://github.com/hyperledger/cacti/pull/2825

Signed-off-by: Michal Bajer michal.bajer@fujitsu.com

Pull Request Requirements

• Rebased onto upstream/main branch and squashed into single commit to help maintainers review it more efficient and to avoid spaghetti git commit graphs that obfuscate which commit did exactly what change, when and, why.
• Have git sign off at the end of commit message to avoid being marked red. You can add -s flag when using git commit command. You may refer to this link for more information.
• Follow the Commit Linting specification. You may refer to this link for more information.

Character Limit

• Pull Request Title and Commit Subject must not exceed 72 characters (including spaces and special characters).
• Commit Message per line must not exceed 80 characters (including spaces and special characters).

A Must Read for Beginners
For rebasing and squashing, here's a must read guide for beginners.

[petermetz]

LGTM

[izuru0]

LGTM