feat: manage bot accounts from the admin UI, API and CLI (#38966)

Adds first-class bot accounts (`UserTypeBot`): local, password-less
users for automation that authenticate only with access tokens.

1. Admin UI: create bots, filter users by type, manage a bot's access
tokens, convert between user and bot
2. API: `POST /admin/users/{username}/convert-type`, and user objects
gain a GitHub-compatible `type` (`User`, `Organization`, `Bot`)
3. CLI: `gitea admin user change-type`, `--user-type` accepts `User` or
`Bot` case-insensitively
4. Converting keeps the password, 2FA, OAuth2 grants and access tokens,
and since sign-in rejects bots, converting back restores the account.
Only local, non-admin accounts can be converted, and conversions are
audited
5. Session, reverse proxy, SSPI, external source and password reset
sign-in reject non-individual users, so a bot never gets an interactive
session
6. Bots receive no notifications or emails

Co-authored-by: Nicolas <bircni@icloud.com>
Co-authored-by: joestump <joe@joestump.net>
Co-authored-by: Joe Stump <joe@stu.mp>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

services/forms/admin.go

@@ -13,9 +13,10 @@ type AdminCreateUserForm struct {
 	middleware.FormDefaultValidator
 	LoginType          string `binding:"Required"`
 	LoginName          string
-	UserName           string `binding:"Required;Username;MaxSize(40)"`
-	Email              string `binding:"Required;Email;MaxSize(254)"`
-	Password           string `binding:"MaxSize(255)"`
+	UserName           string                 `binding:"Required;Username;MaxSize(40)"`
+	UserType           structs.UserTypeString `binding:"In(,User,Bot)"`
+	Email              string                 `binding:"Required;Email;MaxSize(254)"`
+	Password           string                 `binding:"MaxSize(255)"`
 	SendNotify         bool
 	MustChangePassword bool
 	Visibility         structs.VisibleType
@@ -39,8 +40,9 @@ type AdminEditBadgeForm struct {
 // AdminEditUserForm form for admin to create user
 type AdminEditUserForm struct {
 	middleware.FormDefaultValidator
-	LoginType               string `binding:"Required"`
-	UserName                string `binding:"Username;MaxSize(40)"`
+	LoginType               string                 `binding:"Required"`
+	UserType                structs.UserTypeString `binding:"In(,User,Bot)"`
+	UserName                string                 `binding:"Username;MaxSize(40)"`
 	LoginName               string
 	FullName                string `binding:"MaxSize(100)"`
 	Email                   string `binding:"Required;Email;MaxSize(254)"`