Refactor User and DB handling (#123)

fix copyright date

Add more user tests

More user tests

More user tests

Start refactoring user tests

Docs

Fix lint

Fix db fixtures init in tests

Fix models test

Fix loading fixtures

Fix ineffasign

Fix lint

Fix integration tests

Fix init of test engine creation

Fix user related tests

Better handling of creating test enging

Moved all fixtures to db package

Moved all fixtures to db package

Moved user related stuff to seperate package

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/123

docs/content/doc/development/test.md

@@ -42,3 +42,29 @@ The integration tests use the same config and fixtures as the unit tests and the
 see at the beginning of this document.
 
 To run integration tests, use `make integration-test`.
+
+# Initializing db fixtures when writing tests
+
+All db fixtures for all tests live in the `pkg/db/fixtures/` folder as yaml files.
+Each file has the same name as the table the fixtures are for.
+You should put new fixtures in this folder.
+
+When initializing db fixtures, you are responsible for defining which tables your package needs in your test init function.
+Usually, this is done as follows (this code snippet is taken from the `user` package):
+
+```go
+err = db.InitTestFixtures("users")
+if err != nil {
+	log.Fatal(err)
+}
+```
+
+In your actual tests, you then load the fixtures into the in-memory db like so:
+
+```go
+db.LoadAndAssertFixtures(t)
+```
+
+This will load all fixtures you defined in your test init method.
+You should always use this method to load fixtures, the only exception is when your package tests require extra test 
+fixtures other than db fixtures (like files).