Add notes

bounty/src/api/accept.rs

@@ -1,6 +1,7 @@
 use super::state::{Contributor, BOUNTY_STATE};
 
 pub fn accept_impl(contributor: Contributor, github_pr_id: i32) -> () {
+    // FIXME check contributor is the owner of the PR
     BOUNTY_STATE.with(|state| {
         if let Some(ref mut bounty_canister) = *state.borrow_mut() {
             // Add the contributor to the interested contributors list

bounty/src/api/state.rs

@@ -21,6 +21,13 @@ pub struct Contributor {
 }
 
 // Define thread-local storage for the bounty canister state
+// WASM is single-threaded by nature. [RefCell] and [thread_local!] are used despite being not totally safe primitives.
+// This is to ensure that the canister state can be used throughout.
+// Your other option here is to avoid [thread_local!] and use a [RefCell<RwLock/Mutex/Atomic>].
+// Here we use [thread_local!] because it is simpler.
 thread_local! {
+    // Currently, a single canister smart contract is limited to 4 GB of storage due to WebAssembly limitations.
+    // To ensure that our canister does not exceed this limit, we restrict memory usage to at most 2 GB because 
+    // up to 2x memory may be needed for data serialization during canister upgrades.
     pub static BOUNTY_STATE: std::cell::RefCell<Option<BountyState>> = std::cell::RefCell::new(None);
 }