Move internal packages to an internal folder

For reference: https://go.dev/doc/go1.4#internalpackages

internal/ui/oauth2_unlink.go

@@ -0,0 +1,60 @@
+// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package ui // import "miniflux.app/v2/internal/ui"
+
+import (
+	"net/http"
+
+	"miniflux.app/v2/internal/http/request"
+	"miniflux.app/v2/internal/http/response/html"
+	"miniflux.app/v2/internal/http/route"
+	"miniflux.app/v2/internal/locale"
+	"miniflux.app/v2/internal/logger"
+	"miniflux.app/v2/internal/ui/session"
+)
+
+func (h *handler) oauth2Unlink(w http.ResponseWriter, r *http.Request) {
+	printer := locale.NewPrinter(request.UserLanguage(r))
+	provider := request.RouteStringParam(r, "provider")
+	if provider == "" {
+		logger.Info("[OAuth2] Invalid or missing provider")
+		html.Redirect(w, r, route.Path(h.router, "login"))
+		return
+	}
+
+	authProvider, err := getOAuth2Manager(r.Context()).FindProvider(provider)
+	if err != nil {
+		logger.Error("[OAuth2] %v", err)
+		html.Redirect(w, r, route.Path(h.router, "settings"))
+		return
+	}
+
+	sess := session.New(h.store, request.SessionID(r))
+	user, err := h.store.UserByID(request.UserID(r))
+	if err != nil {
+		html.ServerError(w, r, err)
+		return
+	}
+
+	hasPassword, err := h.store.HasPassword(request.UserID(r))
+	if err != nil {
+		html.ServerError(w, r, err)
+		return
+	}
+
+	if !hasPassword {
+		sess.NewFlashErrorMessage(printer.Printf("error.unlink_account_without_password"))
+		html.Redirect(w, r, route.Path(h.router, "settings"))
+		return
+	}
+
+	authProvider.UnsetUserProfileID(user)
+	if err := h.store.UpdateUser(user); err != nil {
+		html.ServerError(w, r, err)
+		return
+	}
+
+	sess.NewFlashMessage(printer.Printf("alert.account_unlinked"))
+	html.Redirect(w, r, route.Path(h.router, "settings"))
+}