fix(CMDBSource): getFieldSpec returns NULL as a string

[Hipska]

Base information

Question	Answer
Related to a SourceForge thread / Another PR / A GitHub Issue / Combodo ticket?	N/A
Type of change?	Bug fix

Symptom

Not able to use ModuleInstallerAPI::MoveColumnInDB when the destination field is not yet present and it is a nullable integer, date, datetime.

Module xxxx : error when calling module installer class xxxx for BeforeDatabaseCreation handler: ModulelId = xxxx, ModuleInstallerClass = xxxx, ModuleInstallerHandler = BeforeDatabaseCreation, ExceptionClass = MySQLException, ExceptionMessage = Failed to issue SQL query: query = ALTER TABLE `ticket` ADD `resolution_date` datetime DEFAULT 'NULL', mysql_errno = 1067, mysql_error = Invalid default value for 'resolution_date'

Reproduction procedure

1. On iTop 3.2.2
2. With PHP 8.3.20
3. Add static::MoveColumnInDB('ticket_request', 'resolution_date', 'ticket', 'resolution_date'); to a installer class.
4. Run setup
5. Finally, see error as above.

Cause

The code in CMDBSource::getFieldSpec makes wrong assumptions.

Proposed solution

First add tests that prove some scenario's fail, then update the mentioned method to better handle NULL defaults.

Test results before change: CMDBSourceTest_testGetFieldSpec.html

Checklist before requesting a review

• I have performed a self-review of my code
• I have tested all changes I made on an iTop instance
• I have added a unit test, otherwise I have explained why I couldn't
• Is the PR clear and detailed enough so anyone can understand without digging in the code?