feature branch: add Psalm static analysis

[COil]

Potential errors found by Psalm and fixed in the main branch

• DTO cleanup, make properties nullable : https://github.com/strangebuzz/MicroSymfony/commit/be4d0fdae6b4a161c122387839af3b19a37ab127
• Fixed internal call in PHPUnit test: https://github.com/strangebuzz/MicroSymfony/commit/d2e7e2fb1a720dd7a005221c31106ccb2c4f0197
• Fixed iterator check in coverage script: https://github.com/strangebuzz/MicroSymfony/commit/eca2f015dc25240d6bd31d6d002a0d68dc821fd8

Links

• https://github.com/vimeo/psalm
• https://github.com/psalm/psalm-plugin-symfony

Status

Q	A
Branch?	feature-branch
Cleanup?	no
Bug fix?	no
Fixed tickets	NA
New feature?	yes
Doc added?	yes
Tests pass?	not yet
Deprecations?	no
License	MIT