Fully separate authentication from IMAP access

Now imapsql module does not handle authentication. (it was not doing it so well
anyway)

sql_table module was introduced and used in the default configuration as
a replacement for functionality that was implemented by imapsql before.

Parts of maddyctl code were rewritten to make it work transparently with
any IMAP backend or credentials store.

Closes #212.

internal/table/sql_query_test.go

@@ -0,0 +1,66 @@
+//+build !nosqlite3,cgo
+
+package table
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/foxcpp/maddy/internal/config"
+	"github.com/foxcpp/maddy/internal/testutils"
+)
+
+func TestSQL(t *testing.T) {
+	path := testutils.Dir(t)
+	mod, err := NewSQL("sql_table", "", nil, nil)
+	if err != nil {
+		t.Fatal("Module create failed:", err)
+	}
+	tbl := mod.(*SQL)
+	err = tbl.Init(config.NewMap(nil, config.Node{
+		Children: []config.Node{
+			{
+				Name: "driver",
+				Args: []string{"sqlite3"},
+			},
+			{
+				Name: "dsn",
+				Args: []string{filepath.Join(path, "test.db")},
+			},
+			{
+				Name: "init",
+				Args: []string{
+					"CREATE TABLE testTbl (key TEXT PRIMARY KEY , value TEXT)",
+					"INSERT INTO testTbl VALUES ('user1', 'user1a')",
+					"INSERT INTO testTbl VALUES ('user3', NULL)",
+				},
+			},
+			{
+				Name: "lookup",
+				Args: []string{"SELECT value FROM testTbl WHERE key = $1"},
+			},
+		},
+	}))
+	if err != nil {
+		t.Fatal("Init failed:", err)
+	}
+
+	check := func(key, res string, ok, fail bool) {
+		t.Helper()
+
+		actualRes, actualOk, err := tbl.Lookup(key)
+		if actualRes != res {
+			t.Errorf("Result mismatch: want %s, got %s", res, actualRes)
+		}
+		if actualOk != ok {
+			t.Errorf("OK mismatch: want %v, got %v", actualOk, ok)
+		}
+		if (err != nil) != fail {
+			t.Errorf("Error mismatch: want failure = %v, got %v", fail, err)
+		}
+	}
+
+	check("user1", "user1a", true, false)
+	check("user2", "", false, false)
+	check("user3", "", false, true)
+}