[#188] Add CredentialsProvider

Signed-off-by: Andrey Berezin <a.berezin@yadro.com>

src/frostfs_testlib/credentials/interfaces.py

@@ -0,0 +1,25 @@
+from abc import abstractmethod
+
+from frostfs_testlib.plugins import load_plugin
+from frostfs_testlib.storage.cluster import ClusterNode
+
+
+class S3CredentialsProvider(object):
+    stash: dict
+
+    def __init__(self, stash: dict) -> None:
+        self.stash = stash
+
+    @abstractmethod
+    def provide(self, cluster_node: ClusterNode) -> tuple[str, str]:
+        raise NotImplementedError("Directly called abstract class?")
+
+
+class CredentialsProvider(object):
+    stash: dict
+    S3: S3CredentialsProvider
+
+    def __init__(self, s3_plugin_name: str) -> None:
+        self.stash = {}
+        s3cls = load_plugin("frostfs.testlib.credentials_providers", s3_plugin_name)
+        self.S3 = s3cls(self.stash)