RUMM-1870 Add data encryption interface

[maxep]

What and why?

Allow users to set custom encryption routines for on-disk data storage.

How?

Expect an implementation of the following protocol:

/// Interface that allows storing data in encrypted format. Encryption/decryption round should
/// return exactly the same data as it given for the encryption originally (even if decryption
/// happens in another process/app launch).
public protocol DataEncryption {
    /// Encrypts given `Data` with user-chosen encryption.
    ///
    /// - Parameter data: Data to encrypt.
    /// - Returns: The encrypted data.
    func encrypt(data: Data) throws -> Data

    /// Decrypts given `Data` with user-chosen encryption.
    ///
    /// Beware that data to decrypt could be encrypted in a previous
    /// app launch, so implementation should be aware of the case when decryption could
    /// fail (for example, key used for encryption is different from key used for decryption, if
    /// they are unique for every app launch).
    ///
    /// - Parameter data: Data to decrypt.
    /// - Returns: The decrypted data.
    func decrypt(data: Data) throws -> Data
}

Review checklist

• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference
• Add CHANGELOG entry for user facing change.

[maxep]

Enforce single byte separator for data splitting during decryption.

[maxep]

Minor refacto

[ncreated]

Everything looks good in code, really well done 👍. I left one blocking feedback on partial mock (it has a bug now).

Also, as we have only add small unit tests in FileWriter (encryption) and FileReader (decryption), but no tests for integration layer, how about adding fuzzy condition to these tests:

• dd-sdk-ios/Tests/DatadogTests/Datadog/RUM/RUMFeatureTests.swift

  Line 96 in 2fd580b

  func testItUsesExpectedPayloadFormatForUploads() throws {

• dd-sdk-ios/Tests/DatadogTests/Datadog/Logging/LoggingFeatureTests.swift

  Line 87 in 2fd580b

  func testItUsesExpectedPayloadFormatForUploads() throws {

• dd-sdk-ios/Tests/DatadogTests/Datadog/Tracing/TracingFeatureTests.swift

  Line 88 in 2fd580b

  func testItUsesExpectedPayloadFormatForUploads() throws {

• dd-sdk-ios/Tests/DatadogTests/Datadog/InternalMonitoring/InternalMonitoringFeatureTests.swift

  Line 87 in 2fd580b

  func testItSendsApplicationAndSDKInfoWithLogs() throws {

in which we could randomize the presence of DataEncryption? Something this:

encryption: Bool.random() ? MockDataEncryption() : nil

These 4 tests assert each feature's payload format on a high level. Their behaviour should remain the same no matter if data encryption is or is not configured.

[ncreated]

Should this be part of Unreleased section along with "Web-view tracking" which is already part 1.10.0-beta1? I think that something is out-of-sync about the CHANGELOG.md, no? IMO the 1.10.0-beta1 release should be listed here as regular release - otherwise we will lose track on what's inside 1.10.0 and what not.

[maxep]

We currently don't add pre-release tag in the changelog, it is part of our release-process. I also think we should add pre-release sections tho! lets chat for updating the process before the next version.

[ncreated]

All good 🚀 👌