Implement Backend Logic for Reporting Period Certification and Transition

[Vikariusu]

Dependencies

Blocked by: #408

Description

Implement the backend logic for certifying (closing) a current reporting period and transitioning to the next one. This includes creating a certification record, updating the organization's current reporting period, and handling edge cases.

Requirements

1. Implement certifyReportingPeriod mutation

This mutation should:
a) Create a new ReportingPeriodCertification (use createReportingPeriodCertification below)
b) Update the organization's current reporting period (use updateCurrentReportingPeriod below)

2. Update existing createReportingPeriodCertification

Ensure it creates a record with:

certifiedBy: current user's id
organizationId: current user's organization id
reportingPeriodId: id of the reporting period being certified

3. Implement updateCurrentReportingPeriod function

This should:
a) Remove the certified period from preferences.current_period_id
b) Set preferences.current_period_id to the result of calling nextReportingPeriod (to implement)

4. Implement nextReportingPeriod query

Find the reporting period with the closest future start date

Business Rules

• Only one reporting period can be open (accepting uploads) at a time
• Users cannot re-certify reporting periods
• Maintain the unique constraint on ReportingPeriodCertification (organizationId + reportingPeriodId)

Edge Cases

Handle scenario when no subsequent reporting period exists. On the frontend, we'll display the last closed period but disable file uploads.