[FEATURE] Create file and folder structure

[cedricziel]

Leverage typo3-console to create the file and folder structure
through composer events.

This also introduces a hash for common scripts which are needed
by the majority of composer-based TYPO3 projects for plumbing scripts that
need to be executed on the to main events that mutate the library state (install && update)

Can also be invoked manually through composer typo3-cms-scripts.

Should be merged back into the next 8.7 release of the dist.

[bmack]

I think flushing cache and set up db structure should be added as well, what do you think?

Could we also describe these actions in the README?

[cedricziel]

Well.. Yes and no :)

I think we should only automate the actions that do not require a db connection, so that CI environments don't necessarily require a db connection. - Even composer create-project would fail if no db connection was available whilst executing the scripts.

Flushing the cache is a good idea, as long as it only handles file caches - the reason is that otherwise no mutating operations with composer would be possible anymore since the post-update scripts would fail and the composer transactions would be rolled back.

I think for those, we should define another script such as typo3-fasten-your-seatbelts or typo3-org-is-not-responsible-for-broken-project.

Jokes aside - there are a bunch of other operations that could be potentially useful such as generating the PackageStates from the set of required extensions and running the extension setup for the active extensions, but we should carefully choose which we want. - Symfony has a competitive advantage in the sense that they use https://packagist.org/packages/incenteev/composer-parameter-handler to ask the user about missing parameters so they have at least a good chance of having the database credentials available.

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I think we should start with the directory structure script and then go from there.

[bmack]

Agreed :) Let's do separate scripts for "t3-deploy" and "t3-setup" etc.

[cedricziel]

Sounds great - thx for the merge!