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>

modules/structs/admin_user.go

@@ -77,3 +77,12 @@ type EditUserOption struct {
 	// User visibility level: public, limited, or private
 	Visibility VisibilityString `json:"visibility" binding:"In(,public,limited,private)"`
 }
+
+// ConvertUserTypeOption options when converting a user between individual and bot
+type ConvertUserTypeOption struct {
+	// The target user type
+	//
+	// required: true
+	// enum: ["User","Bot"]
+	UserType UserTypeString `json:"user_type" binding:"Required;In(User,Bot)"`
+}

modules/structs/user.go

@@ -17,6 +17,8 @@ type User struct {
 	ID int64 `json:"id"`
 	// login of the user, same as `username`
 	UserName string `json:"login"`
+	// the account type
+	Type UserTypeString `json:"type"`
 	// identifier of the user, provided by the external authenticator (if configured)
 	LoginName string `json:"login_name"`
 	// The ID of the user's Authentication Source

modules/structs/user_type.go

@@ -0,0 +1,17 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package structs
+
+// UserTypeString defines the account type as rendered in API responses, webhook payloads and
+// the resulting GitHub Actions event context, where workflows read it as `github.event.sender.type`.
+// The values are capitalized to stay compatible with GitHub, unlike VisibilityString and the other
+// lowercase API enums. The DB representation is user.UserType (int).
+// swagger:enum UserTypeString
+type UserTypeString string
+
+const (
+	UserTypeStringUser         UserTypeString = "User"
+	UserTypeStringOrganization UserTypeString = "Organization"
+	UserTypeStringBot          UserTypeString = "Bot"
+)