docs: add migration guide for v4 to v5

[mairo744]

Q	A
Documentation	yes
Bugfix	no
BC Break	no
New Feature	no
RFC	no
QA	no

Description

This pull request adds a migration guide for users upgrading from version 4 to version 5 of the laminas-hydrator package.

The new guide includes:

• Clear explanation of removed and replaced hydrator classes.
• Notes on removed legacy Zend aliases and how to update plugin manager usage.
• Clarification on removed exceptions and updated SerializableStrategy behavior.
• Recommendations to avoid inheritance and prefer composition or decorators going forward.

[gsteel]

Thanks @mairo744! LGTM. Paging @froschdesign for review too.

[mairo744]

Is there anything I can improve or help with for v5? I'm happy to assist however I can. 😊

[gsteel]

Is there anything I can improve or help with for v5? I'm happy to assist however I can. 😊

Thanks @mairo744 - I'm not overly familiar with this lib, but we will definitely want to at least:

• Update the entire codebase to use native parameter and return types
• Make any improvements to QA tools such as adding composer-require-checker (Example: Setup standalone installation of composer-require-checker laminas-view#274)
• Get dev dependencies upgraded to whatever is supported between PHP 8.1 - 8.4, i.e. Psalm, PHPUnit etc
• Audit require and refactor to avoid soft dependencies, or minimise dependencies where possible
• Fix outstanding issues/bugs
• Reduce the Psalm baseline to as close to zero as possible

[mairo744]

Thank you for the detailed tips — really appreciate it.
I’ll do my best to help with these and I open PRs incrementally as I go. 😊

[froschdesign]

Only small changes are required.

[froschdesign]

LGTM 👍🏻