fix: [SRTP-125] convert epc api in client mode

[and-mora]

Description

This PR proposes to change the mode the openapi generator for epc works. Now the client has been generated instead of the server.
The correct usage for the Api Client is:

import it.gov.pagopa.rtp.activator.client.epc.api.DefaultApi;
...
  var api = new DefaultApi();
  api.postRequestToPayRequests()
...

List of Changes

• change openapi generator for epc to works as client
• converted the configuration properties into a java record
• add concurrency for PR workflows

Motivation and Context

How Has This Been Tested?

• Pre-Deploy Test
  • Unit
  • Integration (Narrow)
• Post-Deploy Test
  • Isolated Microservice
  • Broader Integration
  • Acceptance
  • Performance & Load

Types of changes

• PATCH - Bug fix (backwards compatible bug fixes)
• MINOR - New feature (add functionality in a backwards compatible manner)
• MAJOR - Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[sonarcloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud