[MM-64686] Expose audit logging functionality via plugin API (#31204)

This commit exposes audit logging functionality to plugins via the plugin API, allowing plugins to create and log audit records. Additionally, it addresses a gob encoding issue that could cause plugin crashes when audit data contains nil pointers or unregistered types.

server/public/plugin/audit.go

@@ -0,0 +1,70 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package plugin
+
+import (
+	"encoding/json"
+
+	"github.com/mattermost/mattermost/server/public/model"
+)
+
+// MakeAuditRecord creates a new audit record with basic information for plugin use.
+// This function creates a minimal audit record that can be populated with additional data.
+// Use this when you don't have access to request context or want to manually populate fields.
+func MakeAuditRecord(event string, initialStatus string) *model.AuditRecord {
+	return &model.AuditRecord{
+		EventName: event,
+		Status:    initialStatus,
+		Meta:      make(map[string]any),
+		Actor: model.AuditEventActor{
+			UserId:        "",
+			SessionId:     "",
+			Client:        "",
+			IpAddress:     "",
+			XForwardedFor: "",
+		},
+		EventData: model.AuditEventData{
+			Parameters:  map[string]any{},
+			PriorState:  make(map[string]any),
+			ResultState: make(map[string]any),
+			ObjectType:  "",
+		},
+	}
+}
+
+// MakeAuditRecordWithContext creates a new audit record populated with plugin context information.
+// This is the recommended way for plugins to create audit records when they have request context.
+// The Context should come from plugin hook parameters or HTTP request handlers.
+func MakeAuditRecordWithContext(event string, initialStatus string, ctx *Context, userId, apiPath string) *model.AuditRecord {
+	rec := MakeAuditRecord(event, initialStatus)
+	rec.AddMeta(model.AuditKeyAPIPath, apiPath)
+	rec.Actor.UserId = userId
+	rec.Actor.SessionId = ctx.SessionId
+	rec.Actor.Client = ctx.UserAgent
+	rec.Actor.IpAddress = ctx.IPAddress
+	return rec
+}
+
+func makeAuditRecordGobSafe(record model.AuditRecord) model.AuditRecord {
+	record.EventData.Parameters = makeMapGobSafe(record.EventData.Parameters)
+	record.EventData.PriorState = makeMapGobSafe(record.EventData.PriorState)
+	record.EventData.ResultState = makeMapGobSafe(record.EventData.ResultState)
+	record.Meta = makeMapGobSafe(record.Meta)
+	return record
+}
+
+// makeMapGobSafe converts map data to a gob-safe representation via JSON round-trip.
+// This eliminates problematic types like nil pointers in interfaces that cause gob
+// encoding to fail when sending audit data over RPC via the plugin API.
+func makeMapGobSafe(m map[string]any) map[string]any {
+	jsonBytes, err := json.Marshal(m)
+	if err != nil {
+		return map[string]any{"error": "failed to serialize audit data"}
+	}
+	var gobSafe map[string]any
+	if err := json.Unmarshal(jsonBytes, &gobSafe); err != nil {
+		return map[string]any{"error": "failed to deserialize audit data"}
+	}
+	return gobSafe
+}