fix: Let Representations always have a body

This is relevant when the request has a content-type
but no data.

src/http/representation/BasicRepresentation.ts

@@ -24,6 +24,11 @@ export class BasicRepresentation implements Representation {
   public readonly metadata: RepresentationMetadata;
   public readonly binary: boolean;
 
+  /**
+   * An empty Representation
+   */
+  public constructor();
+
   /**
    * @param data - The representation data
    * @param metadata - The representation metadata
@@ -86,13 +91,15 @@ export class BasicRepresentation implements Representation {
   );
 
   public constructor(
-    data: Readable | any[] | string,
-    metadata: RepresentationMetadata | MetadataRecord | MetadataIdentifier | string,
+    data?: Readable | any[] | string,
+    metadata?: RepresentationMetadata | MetadataRecord | MetadataIdentifier | string,
     metadataRest?: MetadataRecord | string | boolean,
     binary?: boolean,
   ) {
     if (typeof data === 'string' || Array.isArray(data)) {
       data = guardedStreamFrom(data);
+    } else if (!data) {
+      data = guardedStreamFrom([]);
     }
     this.data = guardStream(data);
 
@@ -110,4 +117,11 @@ export class BasicRepresentation implements Representation {
     }
     this.binary = binary;
   }
+
+  /**
+   * Data should only be interpreted if there is a content type.
+   */
+  public get isEmpty(): boolean {
+    return !this.metadata.contentType;
+  }
 }

src/http/representation/Representation.ts

@@ -19,4 +19,10 @@ export interface Representation {
    * (as opposed to complex objects).
    */
   binary: boolean;
+  /**
+   * Whether the data stream is empty.
+   * This being true does not imply that the data stream has a length of more than 0,
+   * only that it is a possibility and should be read to be sure.
+   */
+  isEmpty: boolean;
 }