Check primary keys for all tables and drop ForeignReference (#21721)

Some dbs require that all tables have primary keys, see
- #16802
- #21086

We can add a test to keep it from being broken again.

Edit:

~Added missing primary key for `ForeignReference`~ Dropped the
`ForeignReference` table to satisfy the check, so it closes #21086.

More context can be found in comments.

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: zeripath <art27@cantab.net>

models/db/engine_test.go

@@ -12,6 +12,8 @@ import (
 	"code.gitea.io/gitea/models/unittest"
 	"code.gitea.io/gitea/modules/setting"
 
+	_ "code.gitea.io/gitea/cmd" // for TestPrimaryKeys
+
 	"github.com/stretchr/testify/assert"
 )
 
@@ -51,3 +53,34 @@ func TestDeleteOrphanedObjects(t *testing.T) {
 	assert.NoError(t, err)
 	assert.EqualValues(t, countBefore, countAfter)
 }
+
+func TestPrimaryKeys(t *testing.T) {
+	// Some dbs require that all tables have primary keys, see
+	//   https://github.com/go-gitea/gitea/issues/21086
+	//   https://github.com/go-gitea/gitea/issues/16802
+	// To avoid creating tables without primary key again, this test will check them.
+	// Import "code.gitea.io/gitea/cmd" to make sure each db.RegisterModel in init functions has been called.
+
+	beans, err := db.NamesToBean()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	whitelist := map[string]string{
+		"the_table_name_to_skip_checking": "Write a note here to explain why",
+	}
+
+	for _, bean := range beans {
+		table, err := db.TableInfo(bean)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if why, ok := whitelist[table.Name]; ok {
+			t.Logf("ignore %q because %q", table.Name, why)
+			continue
+		}
+		if len(table.PrimaryKeys) == 0 {
+			t.Errorf("table %q has no primary key", table.Name)
+		}
+	}
+}