Refactor: Move login out of models (#16199)

`models` does far too much. In particular it handles all `UserSignin`.

It shouldn't be responsible for calling LDAP, SMTP or PAM for signing in.

Therefore we should move this code out of `models`.

This code has to depend on `models` - therefore it belongs in `services`.

There is a package in `services` called `auth` and clearly this functionality belongs in there.

Plan:

- [x] Change `auth.Auth` to `auth.Method` - as they represent methods of authentication.
- [x] Move `models.UserSignIn` into `auth`
- [x] Move `models.ExternalUserLogin`
- [x] Move most of the `LoginVia*` methods to `auth` or subpackages
- [x] Move Resynchronize functionality to `auth`
  - Involved some restructuring of `models/ssh_key.go` to reduce the size of this massive file and simplify its files.
- [x] Move the rest of the LDAP functionality in to the ldap subpackage
- [x] Re-factor the login sources to express an interfaces `auth.Source`?
  - I've done this through some smaller interfaces Authenticator and Synchronizable - which would allow us to extend things in future
- [x] Now LDAP is out of models - need to think about modules/auth/ldap and I think all of that functionality might just be moveable
- [x] Similarly a lot Oauth2 functionality need not be in models too and should be moved to services/auth/source/oauth2
  - [x] modules/auth/oauth2/oauth2.go uses xorm... This is naughty - probably need to move this into models.
  - [x] models/oauth2.go - mostly should be in modules/auth/oauth2 or services/auth/source/oauth2 
- [x] More simplifications of login_source.go may need to be done
- Allow wiring in of notify registration -  *this can now easily be done - but I think we should do it in another PR*  - see #16178 
- More refactors...?
  - OpenID should probably become an auth Method but I think that can be left for another PR
  - Methods should also probably be cleaned up  - again another PR I think.
  - SSPI still needs more refactors.* Rename auth.Auth auth.Method
* Restructure ssh_key.go

- move functions from models/user.go that relate to ssh_key to ssh_key
- split ssh_key.go to try create clearer function domains for allow for
future refactors here.

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

cmd/admin.go

@@ -14,7 +14,6 @@ import (
 	"text/tabwriter"
 
 	"code.gitea.io/gitea/models"
-	"code.gitea.io/gitea/modules/auth/oauth2"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/graceful"
 	"code.gitea.io/gitea/modules/log"
@@ -22,6 +21,7 @@ import (
 	repo_module "code.gitea.io/gitea/modules/repository"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/storage"
+	"code.gitea.io/gitea/services/auth/source/oauth2"
 
 	"github.com/urfave/cli"
 )
@@ -597,7 +597,7 @@ func runRegenerateKeys(_ *cli.Context) error {
 	return models.RewriteAllPublicKeys()
 }
 
-func parseOAuth2Config(c *cli.Context) *models.OAuth2Config {
+func parseOAuth2Config(c *cli.Context) *oauth2.Source {
 	var customURLMapping *oauth2.CustomURLMapping
 	if c.IsSet("use-custom-urls") {
 		customURLMapping = &oauth2.CustomURLMapping{
@@ -609,7 +609,7 @@ func parseOAuth2Config(c *cli.Context) *models.OAuth2Config {
 	} else {
 		customURLMapping = nil
 	}
-	return &models.OAuth2Config{
+	return &oauth2.Source{
 		Provider:                      c.String("provider"),
 		ClientID:                      c.String("key"),
 		ClientSecret:                  c.String("secret"),
@@ -625,10 +625,10 @@ func runAddOauth(c *cli.Context) error {
 	}
 
 	return models.CreateLoginSource(&models.LoginSource{
-		Type:      models.LoginOAuth2,
-		Name:      c.String("name"),
-		IsActived: true,
-		Cfg:       parseOAuth2Config(c),
+		Type:     models.LoginOAuth2,
+		Name:     c.String("name"),
+		IsActive: true,
+		Cfg:      parseOAuth2Config(c),
 	})
 }
 
@@ -646,7 +646,7 @@ func runUpdateOauth(c *cli.Context) error {
 		return err
 	}
 
-	oAuth2Config := source.OAuth2()
+	oAuth2Config := source.Cfg.(*oauth2.Source)
 
 	if c.IsSet("name") {
 		source.Name = c.String("name")
@@ -728,7 +728,7 @@ func runListAuth(c *cli.Context) error {
 	w := tabwriter.NewWriter(os.Stdout, c.Int("min-width"), c.Int("tab-width"), c.Int("padding"), padChar, flags)
 	fmt.Fprintf(w, "ID\tName\tType\tEnabled\n")
 	for _, source := range loginSources {
-		fmt.Fprintf(w, "%d\t%s\t%s\t%t\n", source.ID, source.Name, models.LoginNames[source.Type], source.IsActived)
+		fmt.Fprintf(w, "%d\t%s\t%s\t%t\n", source.ID, source.Name, models.LoginNames[source.Type], source.IsActive)
 	}
 	w.Flush()