[chore] Improve empty tag value tests (#22850) (#26036)

**Description:** <Describe what has changed.>

InfluxDB does not allow empty tag values in line protocol. This change
adds a second test to confirm that the InfluxDB exporter does not emit
empty tag values.
    
See #21526 for the original fix to handling empty attribute values. This
PR exists because I forgot I had fixed #21474, then tried to fix #22850
and now realize that #22850 and #21474 are dupes. Live and learn.

**Link to tracking Issue:**

Closes #22850

**Testing:**

**Documentation:**

exporter/influxdbexporter/writer_test.go

@@ -5,8 +5,10 @@ package influxdbexporter
 
 import (
 	"context"
+	"io"
 	"net/http"
 	"net/http/httptest"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -15,6 +17,8 @@ import (
 	"github.com/influxdata/line-protocol/v2/lineprotocol"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/component"
+	"go.opentelemetry.io/collector/config/confighttp"
 )
 
 func Test_influxHTTPWriterBatch_optimizeTags(t *testing.T) {
@@ -141,3 +145,44 @@ func Test_influxHTTPWriterBatch_maxPayload(t *testing.T) {
 		})
 	}
 }
+
+func Test_influxHTTPWriterBatch_EnqueuePoint_emptyTagValue(t *testing.T) {
+	var recordedRequest *http.Request
+	var recordedRequestBody []byte
+	noopHTTPServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if assert.Nil(t, recordedRequest) {
+			recordedRequest = r
+			recordedRequestBody, _ = io.ReadAll(r.Body)
+		}
+	}))
+	t.Cleanup(noopHTTPServer.Close)
+
+	nowTime := time.Unix(1000, 2000)
+
+	influxWriter, err := newInfluxHTTPWriter(
+		new(common.NoopLogger),
+		&Config{
+			HTTPClientSettings: confighttp.HTTPClientSettings{
+				Endpoint: noopHTTPServer.URL,
+			},
+		},
+		component.TelemetrySettings{})
+	require.NoError(t, err)
+	influxWriter.httpClient = noopHTTPServer.Client()
+	influxWriterBatch := influxWriter.NewBatch()
+
+	err = influxWriterBatch.EnqueuePoint(
+		context.Background(),
+		"m",
+		map[string]string{"k": "v", "empty": ""},
+		map[string]interface{}{"f": int64(1)},
+		nowTime,
+		common.InfluxMetricValueTypeUntyped)
+	require.NoError(t, err)
+	err = influxWriterBatch.WriteBatch(context.Background())
+	require.NoError(t, err)
+
+	if assert.NotNil(t, recordedRequest) {
+		assert.Equal(t, "m,k=v f=1i 1000000002000", strings.TrimSpace(string(recordedRequestBody)))
+	}
+}