Holder: SilverStripe 4 compatibility

[robbieaverill]

This is a placeholder for SS4 compat.

I think it would be good to try and merge large changes like renaming files and PSR-2 compatibility in separate pull requests to try and ensure that the Git history remains intact.

Tasks:

• [x] Branch current master off to a new branch for the current latest version and continued support of the current main trunk
• [x] Update the master composer.json alias to the next major version
• [x] PSR-2 linting: #202
• [ ] Rename code to src and the subfolders to PSR-4 compliant equivalents. Add PSR-4 autoloader.
• [ ] Add namespacing and implement throughout the module (core and otherwise), include upgrade mapping file from the upgrader tool
• [ ] Rename templates for namespacing as required
• [ ] Ensure unit tests and CI builds are running (against PHP 5.5 to 7.1)
• [ ] Update documentation, readme, etc

Considerations

• BB code parsing is removed. See silverstripe-archive/silverstripe-bbcodeparser#1 for the decoupled (deprecated module). There are talks about replacing this with markdown during the SS4 upgrade. I think for the initial stage we should get it working on SS4 with minimal regression, then swap it out afterwards.

[robbieaverill]

@dhensby would you mind taking care of the branching and composer alias if you have time?

[dhensby]

I've branched master -> 0.9 so feel free to mess with master as you like

[robbieaverill]

cc @chillu re: our discussion the other day

[sparkcom]

wonder if any progress on this. SS4 now is the default release

[DryerLintPurple]

@sparkcom Given that this hasn't been updated in a year or so, and they killed off the forum on the main Silverstripe website, this package is probably de facto abandonware at this point. Which is a bummer - I had some stuff I was thinking about contributing to it, but I'm not in a position to take over module ownership.

[dhensby]

I'm afraid that now we've retired our forum there's very little need for the core team or SS Ltd to maintain this module.

This module was also problematic as there were a few architectural decisions that have caused some problems that need rethinking (there's a lot of technical debt). It would be good to keep a forum module going, but this module should (or could) probably be stripped down a fair bit if we wanted to keep it maintainable and rework some of that technical debt.

[DryerLintPurple]

What's the technical debt like, anyway? Obviously there's the stuff mentioned above, but are there a lot of other skeletons in the closet?

[dhensby]

I think the technical debt is quite high - If I were inclined to maintain a forum module for SS4 myself I'd strongly consider starting again.

What people consider as "forums" nowadays have moved on quite a bit from a purely linear thread of comments to threaded sets of comments. There's a lot of legacy here in not just technical approach but features as well

[DryerLintPurple]

I'm concerned less about features (I have my own ideas for that stuff) and more about the architectural side, like 'SS modules aren't built that way anymore' type of issues. Other than namespace and PSR-4 stuff, how does that aspect of the code look?