kms: add context.Context to KMS API calls (#15327)

This commit adds a `context.Context` to the
the KMS `{Stat, CreateKey, GenerateKey}` API
calls.

The context will be used to terminate external calls
as soon as the client requests gets canceled.

A follow-up PR will add a `context.Context` to
the remaining `DecryptKey` API call.

Signed-off-by: Andreas Auernhammer <hi@aead.dev>

internal/kms/single-key_test.go

@@ -19,6 +19,7 @@ package kms
 
 import (
 	"bytes"
+	"context"
 	"encoding/base64"
 	"testing"
 )
@@ -29,7 +30,7 @@ func TestSingleKeyRoundtrip(t *testing.T) {
 		t.Fatalf("Failed to initialize KMS: %v", err)
 	}
 
-	key, err := KMS.GenerateKey("my-key", Context{})
+	key, err := KMS.GenerateKey(context.Background(), "my-key", Context{})
 	if err != nil {
 		t.Fatalf("Failed to generate key: %v", err)
 	}