feat(bindings): add Rust RPC client crate (bindings/rust)

bindings/rust/Cargo.toml

@@ -0,0 +1,30 @@
+[package]
+name = "trustlink-client"
+version = "0.1.0"
+edition = "2021"
+description = "Rust RPC client for the TrustLink on-chain attestation contract on Stellar"
+license = "MIT"
+repository = "https://github.com/afurious/TrustLink"
+keywords = ["stellar", "soroban", "attestation", "trustlink", "kyc"]
+categories = ["api-bindings", "web-programming"]
+readme = "README.md"
+
+[dependencies]
+stellar-rpc-client = { version = "21.4.0", package = "stellar-rpc-client" }
+stellar-xdr = { version = "21.2.0", features = ["std", "serde"] }
+stellar-strkey = "0.0.8"
+reqwest = { version = "0.11.27", default-features = false, features = ["json", "rustls-tls"] }
+serde = { version = "1.0.203", features = ["derive"] }
+serde_json = "1.0.120"
+thiserror = "1.0.61"
+tokio = { version = "1.38.0", features = ["rt", "macros"], optional = true }
+hex = "0.4.3"
+base64 = "0.22.1"
+
+[dev-dependencies]
+tokio = { version = "1.38.0", features = ["rt-multi-thread", "macros"] }
+mockito = "1.4.0"
+
+[features]
+default = ["async"]
+async = ["tokio"]

bindings/rust/README.md

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+# trustlink-client
+
+Rust RPC client for the [TrustLink](https://github.com/afurious/TrustLink) on-chain attestation contract on Stellar/Soroban.
+
+This crate is a **thin async HTTP client** that talks to a Soroban RPC node. It is distinct from the on-chain contract crate (`trustlink`) — no Soroban SDK or WASM target is required. It lets Rust backend services, CLIs, and Rust-based indexers query TrustLink without going through a TypeScript or Python SDK.
+
+## Installation
+
+Add to your `Cargo.toml`:
+
+```toml
+[dependencies]
+trustlink-client = { path = "../bindings/rust" }
+tokio = { version = "1", features = ["rt-multi-thread", "macros"] }
+```
+
+## Quick Start
+
+```rust
+use trustlink_client::{TrustLinkClient, Networks};
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let client = TrustLinkClient::new(
+        "CDLZFC3SYJYDZT7K67VZ75HPJVIEUVNIXF47ZG2FB2RMQQVU2HHGCN8",
+        Networks::TESTNET,
+    )?;
+
+    // Check a wallet's KYC status
+    let has_kyc = client
+        .has_valid_claim("GABC...SUBJECT_ADDRESS", "KYC_PASSED")
+        .await?;
+    println!("Has valid KYC: {has_kyc}");
+
+    // Fetch a single attestation by ID
+    let att = client.get_attestation("att_abc123").await?;
+    println!("Claim: {} issued by {}", att.claim_type, att.issuer);
+
+    // Page through all attestations for a subject
+    let page = client
+        .get_subject_attestations("GABC...SUBJECT_ADDRESS", 0, 20)
+        .await?;
+    println!("First page: {} attestations", page.len());
+
+    Ok(())
+}
+```
+
+## API Reference
+
+### Claim verification
+
+| Method | Contract function |
+|---|---|
+| `has_valid_claim(subject, claim_type)` | `has_valid_claim` |
+| `has_valid_claim_from_issuer(subject, claim_type, issuer)` | `has_valid_claim_from_issuer` |
+| `has_any_claim(subject, &[claim_types])` | `has_any_claim` |
+| `has_all_claims(subject, &[claim_types])` | `has_all_claims` |
+
+### Attestation queries
+
+| Method | Contract function |
+|---|---|
+| `get_attestation(id)` | `get_attestation` |
+| `get_attestation_status(id)` | `get_attestation_status` |
+| `get_subject_attestations(subject, offset, limit)` | `get_subject_attestations` |
+| `get_issuer_attestations(issuer, offset, limit)` | `get_issuer_attestations` |
+| `is_issuer(address)` | `is_issuer` |
+| `get_global_stats()` | `get_global_stats` |
+
+### Networks
+
+```rust
+Networks::TESTNET  // https://soroban-testnet.stellar.org
+Networks::MAINNET  // Stellar mainnet RPC
+Networks::LOCAL    // http://localhost:8000/soroban/rpc
+```
+
+Or pass any custom URL string directly to `TrustLinkClient::new`.
+
+## Error handling
+
+All methods return `Result<T, TrustLinkError>`. Contract-level errors (e.g. `NotFound`, `Unauthorized`) surface as `TrustLinkError::Contract` with a typed `ContractErrorCode`:
+
+```rust
+use trustlink_client::{TrustLinkError, ContractErrorCode};
+
+match client.get_attestation("bad_id").await {
+    Ok(att) => println!("{}", att.id),
+    Err(TrustLinkError::Contract { code: ContractErrorCode::NotFound, .. }) => {
+        eprintln!("attestation not found");
+    }
+    Err(e) => eprintln!("error: {e}"),
+}
+```
+
+## Design
+
+All queries are executed as **simulated** (read-only) Soroban transactions via the JSON-RPC `simulateTransaction` endpoint. No signing key or XLM balance is required. The client is a pure async HTTP client — no Soroban SDK runtime or WASM toolchain dependency.
+
+## Testing
+
+```bash
+cd bindings/rust
+cargo test
+```
+
+Tests use `mockito` to stub the Soroban RPC endpoint and run fully offline.
+
+## Relationship to other packages
+
+| Package | Purpose |
+|---|---|
+| `trustlink` (repo root) | On-chain Soroban contract (WASM) |
+| `bindings/rust` (this crate) | **Rust RPC client for off-chain use** |
+| `bindings/typescript` | Auto-generated TypeScript contract bindings |
+| `sdk/typescript` | Higher-level TypeScript SDK |
+| `bindings/python` | Python RPC client |
+
+## License
+
+MIT