feat: enhance file handling with storage key management and retrieval…

[jhonatapers]

This pull request introduces significant changes to how file content is managed and retrieved in the application. The main update is the transition from using a file "location" string to a "storageKey" for identifying file content, and the adoption of streaming file content via InputStream rather than returning a location. This impacts the domain model, application use cases, service interfaces, and related tests. Additionally, the storage service interface is updated to support retrieving content streams, and a new exception is introduced for duplicate storage keys.

Domain model and API changes:

• The Content value object now uses storageKey instead of location, and all validation, construction, and usage have been updated accordingly.
• The GetFileContentOutput now returns an InputStream for file content instead of a location string, reflecting a shift to direct streaming of file content.

Application/service layer changes:

• DefaultGetFileContentUseCase and related logic now use storageKey and retrieve file content via StorageService.retrieve, returning an InputStream to the caller. [1] [2]
• The StorageService interface has been updated: store now returns void and throws if the key exists, delete and retrieve operate on storageKey.
• The file creation flow now generates a random storageKey, retries if a key already exists (using the new StorageKeyAlreadyExistsException), and stores content under that key. [1] [2] [3]

Testing and validation:

• All affected tests have been updated to use storageKey instead of location, and to verify streaming content via InputStream. [1] [2] [3] [4] [5] [6]
• Mocking and assertions in tests have been adapted for the new service interface and content retrieval method. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Infrastructure/API changes:

• The API controller now uses InputStreamResource instead of FileSystemResource to serve file content streams.

Exception handling:

• Introduced StorageKeyAlreadyExistsException to handle rare key collisions when storing content.