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>

tests/integration/integration_test.go

@@ -189,13 +189,8 @@ func getTokenForLoggedInUser(t testing.TB, session *TestSession, scopes ...auth.
 		urlValues.Add("scope-dummy", string(scope)) // it only needs to start with "scope-" to be accepted
 	}
 	req := NewRequestWithURLValues(t, "POST", "/user/settings/applications", urlValues)
-	session.MakeRequest(t, req, http.StatusSeeOther)
-	flashes := session.GetCookieFlashMessage()
-	assert.NotNil(t, flashes)
-	if flashes != nil {
-		return flashes.InfoMsg
-	}
-	return ""
+	resp := session.MakeRequest(t, req, http.StatusOK)
+	return NewHTMLParser(t, resp.Body).Find("#new-access-token-value").Text()
 }
 
 type RequestWrapper struct {