feat: migrate from Cedar to SpiceDB authorization system

This is a major architectural change that replaces the Cedar policy-based
authorization system with SpiceDB's relation-based authorization.

Key changes:

- Migrate from Rust to Go implementation
- Replace Cedar policies with SpiceDB schema and relationships
- Switch from envoy `ext_authz` with Cedar to SpiceDB permission checks
- Update build system and dependencies for Go ecosystem
- Maintain Envoy integration for external authorization

This change enables more flexible permission modeling through SpiceDB's
Google Zanzibar inspired relation-based system, supporting complex
hierarchical permissions that were difficult to express in Cedar.

Breaking change: Existing Cedar policies and Rust-based configuration
will no longer work and need to be migrated to SpiceDB schema.

1 files changed, 0 insertions, 57 deletions

diff --git a/vendor/writeable/README.md b/vendor/writeable/README.md
deleted file mode 100644
index 44138cd7..00000000
--- a/vendor/writeable/README.md
+++ /dev/null
@@ -1,57 +0,0 @@
-# writeable [![crates.io](https://img.shields.io/crates/v/writeable)](https://crates.io/crates/writeable)
-
-<!-- cargo-rdme start -->
-
-`writeable` is a utility crate of the [`ICU4X`] project.
-
-It includes [`Writeable`], a core trait representing an object that can be written to a
-sink implementing `std::fmt::Write`. It is an alternative to `std::fmt::Display` with the
-addition of a function indicating the number of bytes to be written.
-
-`Writeable` improves upon `std::fmt::Display` in two ways:
-
-1. More efficient, since the sink can pre-allocate bytes.
-2. Smaller code, since the format machinery can be short-circuited.
-
-## Examples
-
-```rust
-use std::fmt;
-use writeable::assert_writeable_eq;
-use writeable::LengthHint;
-use writeable::Writeable;
-
-struct WelcomeMessage<'s> {
-    pub name: &'s str,
-}
-
-impl<'s> Writeable for WelcomeMessage<'s> {
-    fn write_to<W: fmt::Write + ?Sized>(&self, sink: &mut W) -> fmt::Result {
-        sink.write_str("Hello, ")?;
-        sink.write_str(self.name)?;
-        sink.write_char('!')?;
-        Ok(())
-    }
-
-    fn writeable_length_hint(&self) -> LengthHint {
-        // "Hello, " + '!' + length of name
-        LengthHint::exact(8 + self.name.len())
-    }
-}
-
-let message = WelcomeMessage { name: "Alice" };
-assert_writeable_eq!(&message, "Hello, Alice!");
-
-// Types implementing `Writeable` are recommended to also implement `fmt::Display`.
-// This can be simply done by redirecting to the `Writeable` implementation:
-writeable::impl_display_with_writeable!(WelcomeMessage<'_>);
-assert_eq!(message.to_string(), "Hello, Alice!");
-```
-
-[`ICU4X`]: ../icu/index.html
-
-<!-- cargo-rdme end -->
-
-## More Information
-
-For more information on development, authorship, contributing etc. please visit [`ICU4X home page`](https://github.com/unicode-org/icu4x).