chore: change to message to warning

Author: vlastahajek

CHANGELOG.md

@@ -1,9 +1,10 @@
 ## [unreleased]
 ### Features
 - [#358](https://github.com/influxdata/influxdb-client-go/pull/358):
-    - Added possibility to set an application name, which will be part of the User-Agent HTTP header
+    - Added possibility to set an application name, which will be part of the User-Agent HTTP header:
         - Set using `Options.SetApplicationName`
-        - Error message is written to log if an application name is not set.
+        - Warning message is written to log if an application name is not set 
+          - This may change to be logged as an error in a future release
     - Added example how to fully override `User-Agent` header using `Doer` interface
 
 ### Bug fixes

client.go

@@ -146,7 +146,7 @@ func NewClientWithOptions(serverURL string, authToken string, options *Options)
 		ilog.Infof("Using URL '%s'%s", serverURL, tokenStr)
 	}
 	if options.ApplicationName() == "" {
-		ilog.Error("Application name is not set")
+		ilog.Warn("Application name is not set")
 	}
 	return client
 }

client_test.go

@@ -7,6 +7,7 @@ package influxdb2
 import (
 	"context"
 	"fmt"
+	ilog "github.com/influxdata/influxdb-client-go/v2/log"
 	"log"
 	"net/http"
 	"net/http/httptest"
@@ -111,7 +112,7 @@ func TestUserAgent(t *testing.T) {
 	var sb strings.Builder
 	log.SetOutput(&sb)
 	log.SetFlags(0)
-	c := NewClient(server.URL, "x")
+	c := NewClientWithOptions(server.URL, "x", DefaultOptions().SetLogLevel(ilog.WarningLevel))
 	assert.True(t, strings.Contains(sb.String(), "Application name is not set"))
 	up, err := c.Ping(context.Background())
 	require.NoError(t, err)