Refactor codebase to replace explicit constructors with Lombok annotations and remove boilerplat (#3415)

# Description of Changes

- **What was changed:**  
- Removed explicit constructor definitions annotated with `@Autowired`
across services, controllers, filters, and schedulers.
- Added Lombok’s `@RequiredArgsConstructor` to automatically generate
required-args constructors and eliminate boilerplate.
- Introduced other Lombok annotations (`@Data`, `@Getter`, `@Setter`,
`@EqualsAndHashCode`, `@NoArgsConstructor`) on model and API classes to
replace manual getters/setters and constructors.
- Standardized string comparisons to use the constant-first form (e.g.,
`"value".equals(variable)`).
- Cleaned up unused imports and organized OpenAPI configuration by
extracting default title/description constants.

- **Why the change was made:**  
  - To reduce repetitive boilerplate code and improve maintainability.  
- To leverage Lombok for cleaner, more consistent dependency injection
and data modeling.
  - To ensure a uniform coding style across the entire codebase.

#3406

---

## Checklist

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code  
- [x] My changes generate no new warnings  

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached  

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#6-testing)
for more details.

src/main/java/stirling/software/SPDF/service/CustomPDFDocumentFactory.java

@@ -19,6 +19,7 @@ import org.apache.pdfbox.pdmodel.PDDocument;
 import org.springframework.stereotype.Component;
 import org.springframework.web.multipart.MultipartFile;
 
+import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 
 import stirling.software.SPDF.model.api.PDFFile;
@@ -29,6 +30,7 @@ import stirling.software.SPDF.model.api.PDFFile;
  */
 @Component
 @Slf4j
+@RequiredArgsConstructor
 public class CustomPDFDocumentFactory {
 
     private final PdfMetadataService pdfMetadataService;
@@ -63,10 +65,6 @@ public class CustomPDFDocumentFactory {
     // Counter for tracking temporary resources
     private static final AtomicLong tempCounter = new AtomicLong(0);
 
-    public CustomPDFDocumentFactory(PdfMetadataService pdfMetadataService) {
-        this.pdfMetadataService = pdfMetadataService;
-    }
-
     /**
      * Main entry point for loading a PDF document from a file. Automatically selects the most
      * appropriate loading strategy.

src/main/java/stirling/software/SPDF/service/MetricsAggregatorService.java

@@ -6,16 +6,18 @@ import java.util.concurrent.ConcurrentHashMap;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.scheduling.annotation.Scheduled;
 import org.springframework.stereotype.Service;
 
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.search.Search;
 
+import lombok.RequiredArgsConstructor;
+
 import stirling.software.SPDF.config.EndpointInspector;
 
 @Service
+@RequiredArgsConstructor
 public class MetricsAggregatorService {
     private static final Logger logger = LoggerFactory.getLogger(MetricsAggregatorService.class);
 
@@ -24,16 +26,6 @@ public class MetricsAggregatorService {
     private final EndpointInspector endpointInspector;
     private final Map<String, Double> lastSentMetrics = new ConcurrentHashMap<>();
 
-    @Autowired
-    public MetricsAggregatorService(
-            MeterRegistry meterRegistry,
-            PostHogService postHogService,
-            EndpointInspector endpointInspector) {
-        this.meterRegistry = meterRegistry;
-        this.postHogService = postHogService;
-        this.endpointInspector = endpointInspector;
-    }
-
     @Scheduled(fixedRate = 7200000) // Run every 2 hours
     public void aggregateAndSendMetrics() {
         Map<String, Object> metrics = new HashMap<>();

src/main/java/stirling/software/SPDF/service/PdfMetadataService.java

@@ -19,7 +19,6 @@ public class PdfMetadataService {
     private final UserServiceInterface userService;
     private final boolean runningProOrHigher;
 
-    @Autowired
     public PdfMetadataService(
             ApplicationProperties applicationProperties,
             @Qualifier("StirlingPDFLabel") String stirlingPDFLabel,

src/main/java/stirling/software/SPDF/service/PostHogService.java

@@ -29,7 +29,6 @@ public class PostHogService {
     private final Environment env;
     private boolean configDirMounted;
 
-    @Autowired
     public PostHogService(
             PostHog postHog,
             @Qualifier("UUID") String uuid,

src/main/java/stirling/software/SPDF/service/misc/ReplaceAndInvertColorService.java

@@ -2,25 +2,22 @@ package stirling.software.SPDF.service.misc;
 
 import java.io.IOException;
 
-import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.core.io.InputStreamResource;
 import org.springframework.stereotype.Service;
 import org.springframework.web.multipart.MultipartFile;
 
+import lombok.RequiredArgsConstructor;
+
 import stirling.software.SPDF.Factories.ReplaceAndInvertColorFactory;
 import stirling.software.SPDF.model.api.misc.HighContrastColorCombination;
 import stirling.software.SPDF.model.api.misc.ReplaceAndInvert;
 import stirling.software.SPDF.utils.misc.ReplaceAndInvertColorStrategy;
 
 @Service
+@RequiredArgsConstructor
 public class ReplaceAndInvertColorService {
     private ReplaceAndInvertColorFactory replaceAndInvertColorFactory;
 
-    @Autowired
-    public ReplaceAndInvertColorService(ReplaceAndInvertColorFactory replaceAndInvertColorFactory) {
-        this.replaceAndInvertColorFactory = replaceAndInvertColorFactory;
-    }
-
     public InputStreamResource replaceAndInvertColor(
             MultipartFile file,
             ReplaceAndInvert replaceAndInvertOption,