add secrets adapter for aws secrets manager

lib/kamal/secrets/adapters/aws_secretsmanager.rb

@@ -0,0 +1,25 @@
+class Kamal::Secrets::Adapters::AwsSecretsmanager < Kamal::Secrets::Adapters::Base
+  private
+    def login(_account)
+      nil
+    end
+
+    def fetch_secrets(secrets, account:, session:)
+      {}.tap do |results|
+        JSON.parse(get_from_secrets_manager(secrets, account: account))["SecretValues"].each do |secret|
+          secret_name = secret["Name"]
+          secret_string = JSON.parse(secret["SecretString"])
+
+          secret_string.each do |key, value|
+            results["#{secret_name}/#{key}"] = value
+          end
+        end
+      end
+    end
+
+    def get_from_secrets_manager(secrets, account:)
+      `aws secretsmanager batch-get-secret-value --secret-id-list #{secrets.map(&:shellescape).join(" ")} --profile #{account}`.tap do
+        raise RuntimeError, "Could not read #{secret} from AWS Secrets Manager" unless $?.success?
+      end
+    end
+end