looking at ways to reduce validator registration calls (#14371)

* looking at ways to reduce validator registration calls

* small mistake, should be epoch start

* adding more optimizations for reducing registration calls while covering more edgecases

* linting

* adding change log and force full push override

* fixing bug and adding tests

* changing if statement just to be safe

* potuz feedback for easier readability

* more review feedback for simplicity

* more review suggestions from potuz

* fix unit test

* reduce redundancy

* Update CHANGELOG.md

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

* small nitpick

* fixing typo

* updating logs

---------

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

api/client/builder/client.go

@@ -278,7 +278,11 @@ func (c *Client) RegisterValidator(ctx context.Context, svr []*ethpb.SignedValid
 	}
 
 	_, err = c.do(ctx, http.MethodPost, postRegisterValidatorPath, bytes.NewBuffer(body))
-	return err
+	if err != nil {
+		return err
+	}
+	log.WithField("num_registrations", len(svr)).Info("successfully registered validator(s) on builder")
+	return nil
 }
 
 var errResponseVersionMismatch = errors.New("builder API response uses a different version than requested in " + api.VersionHeader + " header")