add new functionality and improve backend server structure

- Enhance server functionality and optimize backend code
- Add multi-database support (PostgreSQL, MySQL, SQLite)

server/core_backend-server/apis/health.go

@@ -0,0 +1,53 @@
+package apis
+
+import (
+	"net/http"
+	"slices"
+
+	"github.com/pocketbase/pocketbase/core"
+	"github.com/pocketbase/pocketbase/tools/router"
+)
+
+// bindHealthApi registers the health api endpoint.
+func bindHealthApi(app core.App, rg *router.RouterGroup[*core.RequestEvent]) {
+	subGroup := rg.Group("/health")
+	subGroup.GET("", healthCheck)
+}
+
+// healthCheck returns a 200 OK response if the server is healthy.
+func healthCheck(e *core.RequestEvent) error {
+	resp := struct {
+		Message string         `json:"message"`
+		Code    int            `json:"code"`
+		Data    map[string]any `json:"data"`
+	}{
+		Code:    http.StatusOK,
+		Message: "API is healthy.",
+	}
+
+	if e.HasSuperuserAuth() {
+		resp.Data = make(map[string]any, 3)
+		resp.Data["canBackup"] = !e.App.Store().Has(core.StoreKeyActiveBackup)
+		resp.Data["realIP"] = e.RealIP()
+
+		// loosely check if behind a reverse proxy
+		// (usually used in the dashboard to remind superusers in case deployed behind reverse-proxy)
+		possibleProxyHeader := ""
+		headersToCheck := append(
+			slices.Clone(e.App.Settings().TrustedProxy.Headers),
+			// common proxy headers
+			"CF-Connecting-IP", "Fly-Client-IP", "X‑Forwarded-For",
+		)
+		for _, header := range headersToCheck {
+			if e.Request.Header.Get(header) != "" {
+				possibleProxyHeader = header
+				break
+			}
+		}
+		resp.Data["possibleProxyHeader"] = possibleProxyHeader
+	} else {
+		resp.Data = map[string]any{} // ensure that it is returned as object
+	}
+
+	return e.JSON(http.StatusOK, resp)
+}