feat(contract): add escrow invariant validator and regression tests

.gitignore

@@ -13,4 +13,4 @@ npm-debug.log*
 *.ntvs*
 *.njsproj
 *.sln
-*.sw?
+*.sw?.idx/

apps/onchain/src/fee_tests.rs

@@ -21,7 +21,7 @@ fn create_test_token<'a>(env: &Env, admin: &Address) -> (token::StellarAssetClie
 }
 
 /// Helper function to create token client + admin + address
-fn create_token_contract<'a>(
+pub(crate) fn create_token_contract<'a>(
     env: &Env,
     admin: &Address,
 ) -> (token::Client<'a>, token::StellarAssetClient<'a>, Address) {