refactor: adopt trait-based architecture (FungibleToken, FungibleBurnable, Pausable)

[aguilar1x]

Context

Depends on #3 (import paths). OZ v0.6.0 introduces a trait-based contract architecture. The current contract calls Base::* functions directly inside a monolithic #[contractimpl] block and does not implement any of the standard traits. The new standard requires implementing FungibleToken, FungibleBurnable, and Pausable as separate #[contractimpl] blocks.

Current structure (v0.3.0)

#[contractimpl]
impl MyStablecoin {
    pub fn transfer(env: Env, from: Address, to: Address, amount: i128) { ... }
    pub fn burn(env: Env, from: Address, amount: i128) { ... }
    pub fn pause(env: Env, caller: Address) { ... }
    // ...all methods in one block
}

Target structure (v0.6.0)

#[contractimpl]
impl FungibleToken for MyStablecoin {
    type ContractType = Base;

    #[when_not_paused]
    fn transfer(e: &Env, from: Address, to: MuxedAddress, amount: i128) {
        Self::ContractType::transfer(e, &from, &to, amount);
    }
    // ...
}

#[contractimpl]
impl FungibleBurnable for MyStablecoin {
    #[when_not_paused]
    fn burn(e: &Env, from: Address, amount: i128) {
        Self::ContractType::burn(e, &from, amount);
    }
    // ...
}

#[contractimpl]
impl Pausable for MyStablecoin {
    fn paused(e: &Env) -> bool { pausable::paused(e) }
    fn pause(e: &Env, caller: Address) { /* auth check + pausable::pause(e) */ }
    fn unpause(e: &Env, caller: Address) { /* auth check + pausable::unpause(e) */ }
}

Changes required

• Split the monolithic impl MyStablecoin into multiple impl <Trait> for MyStablecoin blocks
• Implement FungibleToken with type ContractType = Base
• Implement FungibleBurnable
• Implement Pausable (replaces extensions/pausable.rs)
• Remove extensions/burnable.rs, extensions/pausable.rs, extensions/upgradeable.rs — their logic is now covered by the traits
• Keep custom methods (e.g., initialize, mint, batch_mint, get_admin) in a plain impl MyStablecoin block
• Replace if pausable::paused(&env) { return Err(...) } guards with the #[when_not_paused] attribute macro

Reference

See examples/fungible-pausable/src/contract.rs in the OZ repo for the canonical pattern.

Acceptance criteria

• Contract implements FungibleToken, FungibleBurnable, Pausable traits
• extensions/ directory only contains logic not covered by OZ traits
• No manual if pausable::paused checks — use #[when_not_paused] instead
• All existing tests pass

[Joaco2603]

Hi! I’d like to take this issue.

I’ve been working with Soroban and OpenZeppelin-based contracts, and I’m comfortable with trait-based architectures and contract refactoring. This migration from the monolithic #[contractimpl] to the OZ v0.6.0 trait pattern (FungibleToken, FungibleBurnable, Pausable) aligns well with my experience restructuring contracts while preserving behavior and test compatibility.

[anonfedora]

I'm Anonfedora, I'm a Fullstack Blockchain Engr. I'm proficient in Rust (soroban), Rust serverside with Axum and tokio, Nestjs, epxressjs have vast experience in contributing and building on the Stellar ecosystem with the Rust using soroban's SDK.
I'm also good at comprehensively testing features.
ETA: < 12 hours

[Josue19-08]

Hello maintainers 👋

My name is Josué, and I’m a dedicated open-source contributor with hands-on experience building and maintaining production-level applications across Web3 and full-stack ecosystems. My background includes working with Stellar-based infrastructure, Soroban smart contracts, backend services, and modern frontend development using React, with a strong focus on UI structure and user experience.

I’m comfortable navigating the full contribution lifecycle — from understanding the problem and proposing technical solutions, to delivering clean implementations, tests, and well-documented pull requests aligned with the repository’s standards.

This issue strongly matches my skill set, and I believe I can contribute an effective and maintainable solution within a reasonable timeframe. You’re welcome to review my GitHub profile to explore my previous contributions, ongoing open-source work, and technical background.

I care deeply about code quality, scalability, and clear collaboration, and I’m excited about the opportunity to help move this task forward and contribute value to the project.

Thank you for your consideration

[ryzen-xp]

Hi maintainers 👋
I’m a blockchain developer with strong expertise in Stellar, Rust,TS and Stellar SDK integrations. I’ve worked on multiple Stellar-based smart contract and backend systems.

I understand the scope of this issue and can deliver a reliable, production-quality solution with proper tests and documentation.
Plz assign me !!

ETA: 14 hours

[Xoulomon]

Hey maintainers 👋 I’m a blockchain developer with strong expertise in Stellar, Rust,TS and Stellar SDK integrations. I’ve worked on multiple Stellar-based smart contract and backend systems.

I understand the scope of this issue and can deliver a reliable, production-quality solution with proper tests and documentation. And would love to assigned to work on it.

[Chucks1093]

I will split the monolithic impl block into separate trait impls and replace every manual pause check with the #[when_not_paused] attribute macro so the contract fully aligns with OZ v0.6.0. I will have this done the moment it is assigned.