get_interchain: per_chain + chains options (default first anchor per chain); bump 0.5.0

transaction.get_interchain / block.get_interchain take per_chain= and chains=
kwargs mapping to prime-node's ?perChain=&chains= params. Default (no kwargs)
returns one anchor per chain. Shared interchain_query() helper, exported; pytest.

prime_sdk/block.py

@@ -1,6 +1,9 @@
 """Block endpoints."""
 
+from typing import List, Optional
+
 from .client import Client
+from .interchain import interchain_query
 from .models import Block, InterchainTrace
 
 
@@ -11,10 +14,21 @@ class BlockClient:
     def get(self, block_id: str) -> Block:
         return self._client.get(f"/api/v1/block/{block_id}", Block)
 
-    def get_interchain(self, block_id: str) -> InterchainTrace:
+    def get_interchain(
+        self,
+        block_id: str,
+        per_chain: Optional[int] = None,
+        chains: Optional[List[str]] = None,
+    ) -> InterchainTrace:
         """Trace a block to the validator (verification) blocks that validated it
         and the public-chain interchain anchors those validator blocks were
-        bundled into."""
+        bundled into.
+
+        By default returns the first anchor per public chain (anchor proofs are
+        chained, so the earliest per chain is the meaningful one). ``per_chain``
+        caps anchors per chain (1 = first per chain; 0 = all); ``chains``
+        restricts to specific chain ids."""
         return self._client.get(
-            f"/api/v1/block/{block_id}/interchain", InterchainTrace
+            f"/api/v1/block/{block_id}/interchain{interchain_query(per_chain, chains)}",
+            InterchainTrace,
         )