[SELC-5615] feat: added create attachment function

[gianmarcoplutino]

List of Changes

• added buildAttachment function
• added AttachmentTemplate object to ContractTemplate

Motivation and Context

We want to implement the new onboarding flow for GPUs. This new function will allow you to build the PDF of the attachment intended for the PagoPA administrator

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• 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.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

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

See analysis details on SonarQube Cloud