refactor: introduce constants for improved maintainability in tests and server configurations

- Added constants for test endpoints, usernames, and XML headers in client_test.go and device_certificates_test.go to enhance readability and reduce hardcoded values.
- Updated various test cases to utilize these constants, ensuring consistency across tests.
- Refactored imaging settings and server configurations to use defined constants for default values, improving clarity and maintainability in server/device.go and server/imaging.go.
- Enhanced comments throughout the code to clarify functionality and adhere to best practices.

server/ptz_test.go

@@ -7,6 +7,8 @@ import (
 )
 
 // These handlers are better tested through the SOAP handler in integration tests.
+//
+//nolint:unused // Disabled test function kept for reference
 func _DisabledTestHandleGetPresets(t *testing.T) {
 	config := createTestConfig()
 	server, _ := New(config)
@@ -75,6 +77,8 @@ func TestHandleGotoPreset(t *testing.T) {
 }
 
 // TestHandleGetStatus - DISABLED due to SOAP namespace requirements.
+//
+//nolint:unused // Disabled test function kept for reference
 func _DisabledTestHandleGetStatus(t *testing.T) {
 	config := createTestConfig()
 	server, _ := New(config)
@@ -112,6 +116,7 @@ func _DisabledTestHandleGetStatus(t *testing.T) {
 // TestHandleAbsoluteMove - DISABLED due to SOAP namespace requirements
 //
 //nolint:dupl // Disabled test functions have similar structure
+//nolint:unused // Disabled test function kept for reference
 func _DisabledTestHandleAbsoluteMove(t *testing.T) {
 	config := createTestConfig()
 	server, _ := New(config)
@@ -154,6 +159,7 @@ func _DisabledTestHandleAbsoluteMove(t *testing.T) {
 // TestHandleRelativeMove - DISABLED due to SOAP namespace requirements
 //
 //nolint:dupl // Disabled test functions have similar structure
+//nolint:unused // Disabled test function kept for reference
 func _DisabledTestHandleRelativeMove(t *testing.T) {
 	config := createTestConfig()
 	server, _ := New(config)
@@ -196,6 +202,7 @@ func _DisabledTestHandleRelativeMove(t *testing.T) {
 // TestHandleContinuousMove - DISABLED due to SOAP namespace requirements
 //
 //nolint:dupl // Disabled test functions have similar structure
+//nolint:unused // Disabled test function kept for reference
 func _DisabledTestHandleContinuousMove(t *testing.T) {
 	config := createTestConfig()
 	server, _ := New(config)
@@ -236,6 +243,8 @@ func _DisabledTestHandleContinuousMove(t *testing.T) {
 }
 
 // TestHandleStop - DISABLED due to SOAP namespace requirements.
+//
+//nolint:unused // Disabled test function kept for reference
 func _DisabledTestHandleStop(t *testing.T) {
 	config := createTestConfig()
 	server, _ := New(config)