Secondary Service Agreement update functionality

[shafiquech]

Description

At the moment once a secondary service agreement is created it can not be updated via streams. This PR allows updates to secondary service agreement. The change is specifically needed to allow Service Agreement additions modifications along with the rest of the SSA attributes. The feature is configurable and can be enabled or disables by the following flag backbase.stream.legalentity.sink.serviceAgreementUpdateEnabled

Checklist

• [x] I made sure, I read CONTRIBUTING.md to put right branch prefix as per my need.
• [x] I made sure to update CHANGELOG.md.
• [] I made sure to update Stream Wiki(only valid in case of new stream module or architecture changes). ~ N/A
• [x] My changes are adequately tested.
• [x] I made sure all the SonarCloud Quality Gate are passed.

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

92.9% Coverage
0.0% Duplication