refactor: extract template functions into TemplateExtension

- Introduced `TemplateExtension` to encapsulate template functions.
- Moved `static` and `asset` functions from `BlogBuilder` to `TemplateExtension`.
- Adjusted package structure for `TemplateRenderer` and new `TemplateExtension`.

Signed-off-by: Minecon724 <git@m724.eu>

src/main/java/eu/m724/blog/BlogBuilder.java

@@ -3,6 +3,7 @@ package eu.m724.blog;
 import eu.m724.blog.data.Feed;
 import eu.m724.blog.data.Post;
 import eu.m724.blog.data.Site;
+import eu.m724.blog.template.TemplateRenderer;
 import org.apache.commons.io.file.PathUtils;
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.lib.RepositoryBuilder;

src/main/java/eu/m724/blog/template/TemplateExtension.java

@@ -0,0 +1,39 @@
+package eu.m724.blog.template;
+
+import io.pebbletemplates.pebble.extension.AbstractExtension;
+import io.pebbletemplates.pebble.extension.Function;
+import io.pebbletemplates.pebble.template.EvaluationContext;
+import io.pebbletemplates.pebble.template.PebbleTemplate;
+
+import java.util.List;
+import java.util.Map;
+
+public class TemplateExtension extends AbstractExtension {
+    @Override
+    public Map<String, Function> getFunctions() {
+        return Map.of(
+                "static", new Function() {
+                    @Override
+                    public List<String> getArgumentNames() {
+                        return List.of("path");
+                    }
+
+                    @Override
+                    public Object execute(Map<String, Object> args, PebbleTemplate self, EvaluationContext context, int lineNumber) {
+                        return "/static/" + args.get("path"); // TODO for more advanced stuff
+                    }
+                },
+                "asset", new Function() {
+                    @Override
+                    public List<String> getArgumentNames() {
+                        return List.of("path");
+                    }
+
+                    @Override
+                    public Object execute(Map<String, Object> args, PebbleTemplate self, EvaluationContext context, int lineNumber) {
+                        return "/assets/" + args.get("path"); // TODO for more advanced stuff
+                    }
+                }
+        );
+    }
+}

src/main/java/eu/m724/blog/template/TemplateRenderer.java

@@ -1,4 +1,4 @@
-package eu.m724.blog;
+package eu.m724.blog.template;
 
 import eu.m724.blog.data.Post;
 import eu.m724.blog.data.Site;
@@ -35,35 +35,7 @@ public class TemplateRenderer {
 
         var pebbleEngine = new PebbleEngine.Builder()
                 .loader(loader)
-                .extension(new AbstractExtension() {
+                .extension(new TemplateExtension())
-                    @Override
-                    public Map<String, Function> getFunctions() {
-                        return Map.of(
-                                "static", new Function() {
-                                    @Override
-                                    public List<String> getArgumentNames() {
-                                        return List.of("path");
-                                    }
-
-                                    @Override
-                                    public Object execute(Map<String, Object> args, PebbleTemplate self, EvaluationContext context, int lineNumber) {
-                                        return "/static/" + args.get("path"); // TODO for more advanced stuff
-                                    }
-                                },
-                                "asset", new Function() {
-                                    @Override
-                                    public List<String> getArgumentNames() {
-                                        return List.of("path");
-                                    }
-
-                                    @Override
-                                    public Object execute(Map<String, Object> args, PebbleTemplate self, EvaluationContext context, int lineNumber) {
-                                        return "/assets/" + args.get("path"); // TODO for more advanced stuff
-                                    }
-                                }
-                        );
-                    }
-                })
                 .build();
 
         this.indexTemplate = pebbleEngine.getTemplate("index_template");