add bedrock distribution code (#358)

* add bedrock distribution code

* fix linter error

* add bedrock shields support

* linter fixes

* working bedrock safety

* change to return only one violation

* remove env var reading

* refereshable boto credentials

* remove env vars

* address raghu's feedback

* fix session_ttl passing

---------

Co-authored-by: Dinesh Yeduguru <dineshyv@fb.com>

llama_stack/providers/utils/bedrock/client.py

@@ -0,0 +1,76 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+
+import boto3
+from botocore.client import BaseClient
+from botocore.config import Config
+
+from llama_stack.providers.utils.bedrock.config import BedrockBaseConfig
+from llama_stack.providers.utils.bedrock.refreshable_boto_session import (
+    RefreshableBotoSession,
+)
+
+
+def create_bedrock_client(
+    config: BedrockBaseConfig, service_name: str = "bedrock-runtime"
+) -> BaseClient:
+    """Creates a boto3 client for Bedrock services with the given configuration.
+
+    Args:
+        config: The Bedrock configuration containing AWS credentials and settings
+        service_name: The AWS service name to create client for (default: "bedrock-runtime")
+
+    Returns:
+        A configured boto3 client
+    """
+    if config.aws_access_key_id and config.aws_secret_access_key:
+        retries_config = {
+            k: v
+            for k, v in dict(
+                total_max_attempts=config.total_max_attempts,
+                mode=config.retry_mode,
+            ).items()
+            if v is not None
+        }
+
+        config_args = {
+            k: v
+            for k, v in dict(
+                region_name=config.region_name,
+                retries=retries_config if retries_config else None,
+                connect_timeout=config.connect_timeout,
+                read_timeout=config.read_timeout,
+            ).items()
+            if v is not None
+        }
+
+        boto3_config = Config(**config_args)
+
+        session_args = {
+            "aws_access_key_id": config.aws_access_key_id,
+            "aws_secret_access_key": config.aws_secret_access_key,
+            "aws_session_token": config.aws_session_token,
+            "region_name": config.region_name,
+            "profile_name": config.profile_name,
+            "session_ttl": config.session_ttl,
+        }
+
+        # Remove None values
+        session_args = {k: v for k, v in session_args.items() if v is not None}
+
+        boto3_session = boto3.session.Session(**session_args)
+        return boto3_session.client(service_name, config=boto3_config)
+    else:
+        return (
+            RefreshableBotoSession(
+                region_name=config.region_name,
+                profile_name=config.profile_name,
+                session_ttl=config.session_ttl,
+            )
+            .refreshable_session()
+            .client(service_name)
+        )