Add method to read file from storage

Introduced a new `read` method in `storage.service.ts` to fetch files from storage based on checksum, extension, and type. This method handles potential exceptions by throwing a `NotFoundException` if the file is not found.

apps/backend/src/app/storage/storage.service.ts

@@ -177,6 +177,32 @@ export class StorageService {
 		};
 	}
 
+	/**
+	 * Reads a file from storage based on the provided checksum, extension, and type.
+	 *
+	 * @param {string} checksum - The checksum of the file for validation purposes.
+	 * @param {string} extension - The file extension to define the type of file.
+	 * @param {boolean} isDocumentation - A flag to determine if the file is documentation or a regular file.
+	 * @return {Promise<Buffer>} - A promise that resolves to the file data buffer.
+	 * @throws {NotFoundException} - Throws a NotFoundException if the file is not found in storage.
+	 */
+	public async read(
+		checksum: string,
+		extension: string,
+		isDocumentation: boolean
+	) {
+		try {
+			const fileName = `${isDocumentation ? "doc" : "file"}-${checksum}.${extension.toLowerCase()}`;
+			console.log(`Fetching file "${fileName}" from storage...`);
+			const file = await this.getFile(fileName)
+			console.log(`Got a ${file.byteLength / (1024 * 1024)}MiB file from the storage.`)
+			return file;
+		} catch (err) {
+			console.log("File not found.")
+			throw new NotFoundException(err);
+		}
+	}
+
 	/**
 	 * Processes and saves a new file after validating its properties and conditions.
 	 *