(Fixes #63 and #66) Fix Mime Related Security Issues (#95)

Author: dannym-arx

crates/mdk-core/CHANGELOG.md

@@ -90,7 +90,9 @@
 - **Security (Audit Issue Q)**: Fixed `remove_members` to use actual leaf indices from the ratchet tree instead of enumeration indices. Previously, using `enumerate()` to derive `LeafNodeIndex` caused removal of incorrect members when the tree had holes from prior removals. Now uses `member.index` directly. ([#120](https://github.com/marmot-protocol/mdk/pull/120))
 - **Security (Audit Issue R)**: Refactor encoding handling to enforce base64 usage for key packages and welcome ([#98](https://github.com/marmot-protocol/mdk/pull/98))
 - **Security (Audit Issue S)**: Added validation for mandatory `relays` tag in MLS KeyPackage events. The `validate_key_package_tags` function now requires a `relays` tag with at least one valid relay URL, preventing acceptance of unroutable key packages that could cause delivery failures or enable denial-of-service attacks. ([#118](https://github.com/marmot-protocol/mdk/pull/118))
+- **Security (Audit Issue T)**: Fixed incomplete MIME type canonicalization in `validate_mime_type` ([#95](https://github.com/marmot-protocol/mdk/pull/110))
 - **Security (Audit Issue U)**: Fixed deterministic nonce derivation that caused nonce reuse and message linkability. Encryption now uses random nonces per encryption operation, stored in the IMETA tag. The nonce field (`n`) is now required in IMETA tags. ([#114](https://github.com/marmot-protocol/mdk/pull/114))
+- **Security (Audit Issue W)**: Added MIME type validation and allowlist enforcement ([#95](https://github.com/marmot-protocol/mdk/pull/110))
 - **Security (Audit Issue Y)**: Encrypted media keys and nonces now use `Secret<T>` wrapper for automatic memory zeroization, preventing sensitive cryptographic material from persisting in memory ([#109](https://github.com/marmot-protocol/mdk/pull/109))
 - **Security (Audit Issue Z)**: Added pagination to prevent memory exhaustion from unbounded loading of group messages ([#111](https://github.com/marmot-protocol/mdk/pull/111))
 - **Security (Audit Issue AA)**: Added pagination to prevent memory exhaustion from unbounded loading of pending welcomes ([#110](https://github.com/marmot-protocol/mdk/pull/110))