feat: complete XMPP bridge implementation with configuration fixes

- Fix configuration loading by matching JSON field names with plugin manifest keys
- Move configuration to separate package to resolve type conflicts
- Implement bridge startup logic that initializes on OnActivate and updates on OnConfigurationChange
- Add certificate verification skip option for development/testing environments
- Create XMPP client initialization helper function to avoid code duplication
- Add SetOnlinePresence() method to XMPP client for presence management
- Set bridge user online presence automatically upon successful XMPP connection
- Remove unused mock generation and test files as requested
- Update bridge constructor to accept configuration parameter
- Implement proper bridge lifecycle management with Start/Stop methods

The bridge now properly loads configuration from admin console, creates XMPP connections
with appropriate TLS settings, and manages online presence for the bridge user.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

server/logger/logger.go

@@ -0,0 +1,41 @@
+package logger
+
+import "github.com/mattermost/mattermost/server/public/plugin"
+
+// Logger interface for logging operations
+type Logger interface {
+	LogDebug(message string, keyValuePairs ...any)
+	LogInfo(message string, keyValuePairs ...any)
+	LogWarn(message string, keyValuePairs ...any)
+	LogError(message string, keyValuePairs ...any)
+}
+
+// PluginAPILogger adapts the plugin.API to implement the Logger interface
+type PluginAPILogger struct {
+	api plugin.API
+}
+
+// NewPluginAPILogger creates a new PluginAPILogger
+func NewPluginAPILogger(api plugin.API) Logger {
+	return &PluginAPILogger{api: api}
+}
+
+// LogDebug logs a debug message
+func (l *PluginAPILogger) LogDebug(message string, keyValuePairs ...any) {
+	l.api.LogDebug(message, keyValuePairs...)
+}
+
+// LogInfo logs an info message
+func (l *PluginAPILogger) LogInfo(message string, keyValuePairs ...any) {
+	l.api.LogInfo(message, keyValuePairs...)
+}
+
+// LogWarn logs a warning message
+func (l *PluginAPILogger) LogWarn(message string, keyValuePairs ...any) {
+	l.api.LogWarn(message, keyValuePairs...)
+}
+
+// LogError logs an error message
+func (l *PluginAPILogger) LogError(message string, keyValuePairs ...any) {
+	l.api.LogError(message, keyValuePairs...)
+}