feat(router): support hive as source for supergraph (#400)

feat(router): support `poll_interval` in `file` source for supergraph
feat(router): added HTTP `/readiness` check

Author: dotansimha

.github/workflows/ci.yaml

@@ -25,6 +25,10 @@ jobs:
       - uses: actions-rust-lang/setup-rust-toolchain@1780873c7b576612439a134613cc4cc74ce5538c # v1
       - run: cargo test_all
       - run: cargo test_e2e
+        timeout-minutes: 5
+        env:
+          RUST_BACKTRACE: full
+          RUST_LOG: debug
 
   build-release:
     name: cargo build