Adding realworld test dataset

[s3inlc]

This adds two database testsets which are prefilled with some data for most of the tables. This allows more complex tests to be done without having to fill in a lot of test data (especially for GET queries).

There are three kind of tests then:

• synthetic only: only tested starting with an empty database and then filled with what is needed during the test
• realworld only: only tested with the pre-populated databases, testing some specifics only possible with some larger pre-filled data
• both: most of the simpler tests can be executed with both, also then making sure that they work with data existing and empty data as well

[Copilot]

Pull request overview

This PR introduces a “realworld” pre-populated database dataset for CI and adds smoke/pagination tests that validate API behavior against that larger, realistic data shape. It also wires dataset selection into pytest so tests can be run against either an empty (synthetic) DB or the realworld dump.

Changes:

• Add a realworld pytest marker + --test-dataset switch to selectively run/skip tests depending on dataset.
• Add realworld smoke tests validating known counts, relationships, and pagination behavior on large tables.
• Extend CI and the start action to import DB dumps and run the test suite against both MySQL and Postgres realworld datasets.

Reviewed changes

Copilot reviewed 8 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
ci/testdata/config.json	Adds dataset-specific config (PEPPER) intended to match the dump.
ci/apiv2/test_realworld_dump.py	New realworld-only smoke/pagination tests against the dump dataset.
ci/apiv2/test_permissions.py	Marks a test as synthetic-only to avoid running it on prefilled DB.
ci/apiv2/test_file.py	Marks a test as synthetic-only to avoid running it on prefilled DB.
ci/apiv2/conftest.py	Adds --test-dataset option + marker-based skipping logic.
.github/workflows/ci.yml	Adds a new realworld CI job for MySQL/Postgres.
.github/scripts/import-testdata-dump.sh	New script to install config + import MySQL/Postgres dumps.
.github/actions/start-hashtopolis/action.yml	Adds test_dataset input and realworld import/start sequence.

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