feat: cm as precipitation unit

This will be useful for daily/hourly units classes.
The param method translates cm to mm, useful when it's an endpoint parameter.

Author: DadiBit

lib/src/main/kotlin/com/openmeteo/api/common/params/PrecipitationUnit.kt

@@ -1,9 +1,18 @@
 package com.openmeteo.api.common.params
 
 /**
- * The unit that should be used for precipitation
+ * The unit used for precipitations
+ *
+ * When used as an endpoint parameter cm "becomes" mm through `?.param()`
  */
 enum class PrecipitationUnit {
+    cm,
     mm,
-    inch,
+    inch;
+
+    /**
+     * Called only when the unit is used as parameter
+     */
+    fun param() =
+        takeUnless { it == cm } ?: mm
 }

lib/src/main/kotlin/com/openmeteo/api/ecmwf/EcmwfEndpoint.kt

@@ -29,7 +29,7 @@ class EcmwfEndpoint(
         "hourly" to hourly?.joinToString(","),
         "temperature_unit" to temperatureUnit,
         "windspeed_unit" to windSpeedUnit,
-        "precipitation_unit" to precipitationUnit,
+        "precipitation_unit" to precipitationUnit?.param(),
         "timeformat" to TimeFormat.unixtime,
         "past_days" to pastDays?.takeIf { it in 0..2 },
         "start_date" to startDate,

lib/src/main/kotlin/com/openmeteo/api/forecast/ForecastEndpoint.kt

@@ -36,7 +36,7 @@ class ForecastEndpoint(
         "current_weather" to currentWeather,
         "temperature_unit" to temperatureUnit,
         "windspeed_unit" to windSpeedUnit,
-        "precipitation_unit" to precipitationUnit,
+        "precipitation_unit" to precipitationUnit?.param(),
         "timeformat" to TimeFormat.unixtime,
         "timezone" to (timeZone ?: daily?.let { "auto" }),
         "past_days" to pastDays?.takeIf { it in 0..2 },

lib/src/main/kotlin/com/openmeteo/api/historical/HistoricalEndpoint.kt

@@ -35,7 +35,7 @@ class HistoricalEndpoint(
         "daily" to daily?.joinToString(","),
         "temperature_unit" to temperatureUnit,
         "windspeed_unit" to windSpeedUnit,
-        "precipitation_unit" to precipitationUnit,
+        "precipitation_unit" to precipitationUnit?.param(),
         "timeformat" to TimeFormat.unixtime,
         "timezone" to (timeZone ?: daily?.let { "auto" }),
     )