fix: surface readable error when server app exception cannot be deserialized

[David-Development]

Problem

When a request fails inside the Files app, InputStreamBinder serializes the original exception object over the AIDL pipe. If the exception's class — or any class in its cause chain — only exists in the Files app (e.g. com.owncloud.android.lib.common.network.CertificateCombinedException on SSL/certificate errors), ObjectInputStream#readObject in AidlNetworkRequest#deserializeObjectV2 throws a ClassNotFoundException in the client app.

The real error is completely lost, and client apps end up showing something like:

java.lang.ClassNotFoundException: com.owncloud.android.lib.common.net...

See nextcloud/news-android#1645 for a report of exactly this (expired SSL certificate → cryptic ClassNotFoundException in the News app).

Fix

Catch the ClassNotFoundException during exception deserialization and replace it with a plain exception that carries the original type name plus a hint to check the server connection. It then flows through the existing SSOException#parseNextcloudCustomException translation, so client apps receive a proper SSOException (UnknownErrorException) and show their regular error dialog instead of a raw ClassNotFoundException.

This is the receiver-side safety net and works against all already-shipped Files app versions. Follow-up (separate PR in nextcloud/android): flatten exceptions to plain JRE types in InputStreamBinder#serializeObjectToInputStreamV2 before serializing, so the original error message survives the IPC as well, not just the type name.

Tests

Added AidlNetworkRequestTest:

• missing-class scenario: serializes a real exception, then byte-patches its class name in the serialized stream to a nonexistent one — reproducing exactly what happens over the IPC channel; asserts a readable exception (not ClassNotFoundException) containing the original type name is returned
• happy path: null exception + headers are still parsed correctly
• deserializable exceptions still pass through unchanged

🤖 Generated with Claude Code

[github-actions]

SpotBugs

Category	Base	New
Bad practice	9	9
Correctness	24	24
Dodgy code	13	13
Internationalization	2	2
Malicious code vulnerability	11	11
Multithreaded correctness	4	4
Performance	4	4
Security	7	7
Total	74	74

[codacy-production]

Not up to standards ⛔

🔴 Issues 3 minor

Alerts:
⚠ 3 issues (≤ 0 issues of at least minor severity)

Results:
3 new issues

Category	Results
CodeStyle	3 minor

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🟢 Metrics 10 complexity

Metric	Results
Complexity	10

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