[Refactor] unexport config.Config var & move login tasks to task module (#288)

Unexport generateToken()

move CreateLogin into task

Create func config.SetDefaultLogin()

Unexport loadConfig() & saveConfig

unexport config var

make SetDefaultLogin() case insensitive

update func descriptions

move FindSSHKey to task module

Reviewed-on: https://gitea.com/gitea/tea/pulls/288
Reviewed-by: Norwin <noerw@noreply.gitea.io>
Reviewed-by: Andrew Thornton <art27@cantab.net>
Co-Authored-By: 6543 <6543@obermui.de>
Co-Committed-By: 6543 <6543@obermui.de>

cmd/login/edit.go

@@ -21,6 +21,6 @@ var CmdLoginEdit = cli.Command{
 	Flags:       []cli.Flag{&flags.OutputFlag},
 }
 
-func runLoginEdit(ctx *cli.Context) error {
+func runLoginEdit(_ *cli.Context) error {
 	return open.Start(config.GetConfigPath())
 }