Allow colons in the prometheus metric name (#6751)

plugins/serializers/prometheus/prometheus_test.go

@@ -409,6 +409,42 @@ rpc_duration_seconds_count 2693
 # HELP cpu_time_idle Telegraf collected metric
 # TYPE cpu_time_idle untyped
 cpu_time_idle 43
+`),
+		},
+		{
+			name: "colons are not replaced in metric name from measurement",
+			metrics: []telegraf.Metric{
+				testutil.MustMetric(
+					"cpu::xyzzy",
+					map[string]string{},
+					map[string]interface{}{
+						"time_idle": 42.0,
+					},
+					time.Unix(0, 0),
+				),
+			},
+			expected: []byte(`
+# HELP cpu::xyzzy_time_idle Telegraf collected metric
+# TYPE cpu::xyzzy_time_idle untyped
+cpu::xyzzy_time_idle 42
+`),
+		},
+		{
+			name: "colons are not replaced in metric name from field",
+			metrics: []telegraf.Metric{
+				testutil.MustMetric(
+					"cpu",
+					map[string]string{},
+					map[string]interface{}{
+						"time:idle": 42.0,
+					},
+					time.Unix(0, 0),
+				),
+			},
+			expected: []byte(`
+# HELP cpu_time:idle Telegraf collected metric
+# TYPE cpu_time:idle untyped
+cpu_time:idle 42
 `),
 		},
 		{
@@ -429,6 +465,26 @@ cpu_time_idle 43
 # HELP cpu_time_idle Telegraf collected metric
 # TYPE cpu_time_idle untyped
 cpu_time_idle{host_name="example.org"} 42
+`),
+		},
+		{
+			name: "colons are replaced in label name",
+			metrics: []telegraf.Metric{
+				testutil.MustMetric(
+					"cpu",
+					map[string]string{
+						"host:name": "example.org",
+					},
+					map[string]interface{}{
+						"time_idle": 42.0,
+					},
+					time.Unix(0, 0),
+				),
+			},
+			expected: []byte(`
+# HELP cpu_time_idle Telegraf collected metric
+# TYPE cpu_time_idle untyped
+cpu_time_idle{host_name="example.org"} 42
 `),
 		},
 		{