Add config flow for Utility Meter (#22180)

Co-authored-by: Erik Montnemery <erik@montnemery.com>

source/_integrations/utility_meter.markdown

@@ -6,6 +6,7 @@ ha_category:
 ha_release: 0.87
 ha_iot_class: Local Push
 ha_quality_scale: internal
+ha_config_flow: true
 ha_codeowners:
   - '@dgomes'
 ha_domain: utility_meter
@@ -13,7 +14,7 @@ ha_platforms:
   - sensor
 ---
 
-The `utility meter` integration provides functionality to track consumptions of various utilities (e.g., energy, gas, water, heating).
+The Utility Meter integration provides functionality to track consumptions of various utilities (e.g., energy, gas, water, heating).
 
 From a user perspective, utility meters operate in cycles (usually monthly) for billing purposes. This sensor will track a source sensor values, automatically resetting the meter based on the configured cycle. On reset an attribute will store the previous meter value, providing the means for comparison operations (e.g., "did I spend more or less this month?") or billing estimation (e.g., through a sensor template that multiplies the metered value per the charged unit amount).
 
@@ -23,9 +24,44 @@ Some utility providers have different tariffs according to time/resource availab
 Sensors created with this integration are persistent, so values are retained across restarts of Home Assistant. The first cycle for each sensor will be incomplete; a sensor tracking daily usage will start to be accurate the next day after the integration was activated. A sensor tracking monthly usage will present accurate data starting the first of the next month after being added to Home Assistant.
 </div>
 
-## Configuration
+{% include integrations/config_flow.md %}
+{% configuration_basic %}
+Name:
+  description: The name the sensor should have. It can be changed again later.
+Input sensor:
+  description: The sensor entity providing utility readings (energy, water, gas, heating).
+Meter reset cycle:
+  description: >
+    How often to reset the counter. If the offered reset cycles do not match
+    your use case, consider using the YAML configuration below, which allows
+    for creating CRON-style patterns.
+Meter reset offset:
+  description: >
+    Cycle reset occur at the beginning of the period. This option enables
+    the offsetting of these beginnings, counted in days. If you need a more
+    fine-grained offset, consider using the YAML configuration below, which
+    allows for that.
+Supported tariffs:
+  description: >
+    A list of supported tariffs, leave empty if only a single tariff is needed.
+Net consumption:
+  description: >
+    Enable this if you would like to treat the source as a net meter.
+    This will allow your counter to go both positive and negative.
+Delta values:
+  description: >
+    Enable this if the source values are delta values since the last reading instead of absolute values. When this option is enabled, each new value received will be added as-is to the utility meter instead of adding the _difference_ between the new value and previous value.
+{% endconfiguration_basic %}
 
-To enable the Utility Meter Sensor in your installation, add the following to your `configuration.yaml` file:
+If the meter reset cycle and reset offsets are to limited for your use case,
+consider using the YAML configuration below, which support CRON-style patterns
+that provide a greater flexibility.
+
+## YAML Configuration
+
+Alternatively, this integration can be configured and set up manually via YAML
+instead. To enable the Integration sensor in your installation, add the
+following to your `configuration.yaml` file:
 
 ```yaml
 # Example configuration.yaml entry