Add Prometheus metrics relabeling (#3734)

Co-authored-by: Guillermo Ruffino <glm.net@gmail.com>

esphome/components/prometheus/__init__.py

@@ -2,16 +2,27 @@ import esphome.config_validation as cv
 import esphome.codegen as cg
 from esphome.const import (
     CONF_ID,
+    CONF_NAME,
     CONF_INCLUDE_INTERNAL,
+    CONF_RELABEL,
 )
 from esphome.components.web_server_base import CONF_WEB_SERVER_BASE_ID
 from esphome.components import web_server_base
+from esphome.cpp_types import EntityBase
 
 AUTO_LOAD = ["web_server_base"]
 
 prometheus_ns = cg.esphome_ns.namespace("prometheus")
 PrometheusHandler = prometheus_ns.class_("PrometheusHandler", cg.Component)
 
+CUSTOMIZED_ENTITY = cv.Schema(
+    {
+        cv.Optional(CONF_ID): cv.string_strict,
+        cv.Optional(CONF_NAME): cv.string_strict,
+    },
+    cv.has_at_least_one_key,
+)
+
 CONFIG_SCHEMA = cv.Schema(
     {
         cv.GenerateID(): cv.declare_id(PrometheusHandler),
@@ -19,6 +30,11 @@ CONFIG_SCHEMA = cv.Schema(
             web_server_base.WebServerBase
         ),
         cv.Optional(CONF_INCLUDE_INTERNAL, default=False): cv.boolean,
+        cv.Optional(CONF_RELABEL, default={}): cv.Schema(
+            {
+                cv.use_id(EntityBase): CUSTOMIZED_ENTITY,
+            }
+        ),
     },
     cv.only_with_arduino,
 ).extend(cv.COMPONENT_SCHEMA)
@@ -33,3 +49,10 @@ async def to_code(config):
     await cg.register_component(var, config)
 
     cg.add(var.set_include_internal(config[CONF_INCLUDE_INTERNAL]))
+
+    for key, value in config[CONF_RELABEL].items():
+        entity = await cg.get_variable(key)
+        if CONF_ID in value:
+            cg.add(var.add_label_id(entity, value[CONF_ID]))
+        if CONF_NAME in value:
+            cg.add(var.add_label_name(entity, value[CONF_NAME]))