pkg/currency: Add error tags on currency exchange errors

[Sypheos]

What does this PR do?

Add error tags and wrapping for currency exchange to make debugging easier

What are the observable changes?

Good PR checklist

• Title makes sense
• Is against the correct branch
• Only addresses one issue
• Properly assigned
• Added/updated tests
• Added/updated documentation
• Properly labeled

Additional Notes

[AlexisMontagne]

no private 🙈

[AlexisMontagne]

when i said, no private i meant you can use the public action: https://github.com/upfluence/actions/blob/master/.github/workflows/lib-go-test.yml

[AlexisMontagne]

Can you attach the following diff to fix the CI?

diff --git a/syncutil/singleflight_test.go b/syncutil/singleflight_test.go
index 14a11ec..514ffd3 100644
--- a/syncutil/singleflight_test.go
+++ b/syncutil/singleflight_test.go
@@ -114,6 +114,7 @@ func TestSingleflightStopOnClose(t *testing.T) {
 	var (
 		sf  Singleflight
 		ctr int32
+		wg  sync.WaitGroup
 
 		ctx   = context.Background()
 		donec = make(chan struct{})
@@ -130,17 +131,23 @@ func TestSingleflightStopOnClose(t *testing.T) {
 		return nil
 	}
 
+	wg.Add(1)
+
 	go func() {
 		ok, err := sf.Do(ctx, fn)
 
 		assert.True(t, ok)
 		assert.Equal(t, context.Canceled, err)
+
+		wg.Done()
 	}()
 
 	time.Sleep(10 * time.Millisecond)
 
+	sf.Close()
 	close(donec)
-	assert.Equal(t, int32(0), atomic.LoadInt32(&ctr))
 
-	sf.Close()
+	wg.Wait()
+
+	assert.Equal(t, int32(0), atomic.LoadInt32(&ctr))
 }