~So the MVP is to use existing code to write to the data blob. When this story is discussed I'd like to consider the options of storing this data in a separate table, as proposed by T134327. At least as an additional place where data is stored, to pave the way for future migration. ~

Update While discussing this, we agreed to *not* store the tracking data as another blob, but create database tables for it.

Note to self: consider using Matomo for this.

We have discussed how to implement this issue and concluded that Matomo is not a good fit for the intended use case for various reasons, mainly because the data on Matomo is relatively incomplete and cannot easily be matched to actual donations / membership applications.

For that reason, the tracking implementation should make use of the application database. The storing of data should utilize a repository interface similar to DonationRepository in fundraising-donations, for example. The repository class and its implementation should be placed in FundraisingFrontend; the interface itself should be placed in BucketTesting while the implementation should be placed in a new DataAccess directory in src/. The database can be queried directly, no ORM must be used in order to keep the complexity down.

The table structure could be two tables in a 1:n relationship, where 1 tracking_event has n buckets (possibly 0?) attached to it. Any database migrations should make use of Doctrine Migrations and should be placed in the FundraisingFrontend repository directly.

This ticket needs to be re-estimated, because the database changes and database layer stuff should not be put into FundraisingStore, but rather in Fundraising\Frontend\BucketTesting\DataAccess. Furthermore, we need to add another migration script (luckily we don't need referential integrity between tracking and donation/memberships) and add the migration to the Makefile.

Reduced the story points, because this task will not cover the database persistence.

WIP of how I imagine this to work is up: https://github.com/wmde/FundraisingFrontend/pull/1310

PR is finished and can be reviewed. I've added documentation on how to process the "log" file.