Provide the ability to set password hash algorithm parameters (#22942) (#22943)

Backport #22942

This PR refactors and improves the password hashing code within gitea
and makes it possible for server administrators to set the password
hashing parameters

In addition it takes the opportunity to adjust the settings for `pbkdf2`
in order to make the hashing a little stronger.

The majority of this work was inspired by PR #14751 and I would like to
thank @boppy for their work on this.

Thanks to @gusted for the suggestion to adjust the `pbkdf2` hashing
parameters.

Close #14751

---------

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

modules/auth/password/hash/setting_test.go

@@ -0,0 +1,38 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package hash
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCheckSettingPasswordHashAlgorithm(t *testing.T) {
+	t.Run("pbkdf2 is pbkdf2_v2", func(t *testing.T) {
+		pbkdf2v2Config, pbkdf2v2Algo := SetDefaultPasswordHashAlgorithm("pbkdf2_v2")
+		pbkdf2Config, pbkdf2Algo := SetDefaultPasswordHashAlgorithm("pbkdf2")
+
+		assert.Equal(t, pbkdf2v2Config, pbkdf2Config)
+		assert.Equal(t, pbkdf2v2Algo.Name, pbkdf2Algo.Name)
+	})
+
+	for a, b := range aliasAlgorithmNames {
+		t.Run(a+"="+b, func(t *testing.T) {
+			aConfig, aAlgo := SetDefaultPasswordHashAlgorithm(a)
+			bConfig, bAlgo := SetDefaultPasswordHashAlgorithm(b)
+
+			assert.Equal(t, bConfig, aConfig)
+			assert.Equal(t, aAlgo.Name, bAlgo.Name)
+		})
+	}
+
+	t.Run("pbkdf2_v2 is the default when default password hash algorithm is empty", func(t *testing.T) {
+		emptyConfig, emptyAlgo := SetDefaultPasswordHashAlgorithm("")
+		pbkdf2v2Config, pbkdf2v2Algo := SetDefaultPasswordHashAlgorithm("pbkdf2_v2")
+
+		assert.Equal(t, pbkdf2v2Config, emptyConfig)
+		assert.Equal(t, pbkdf2v2Algo.Name, emptyAlgo.Name)
+	})
+}