Extract building relations

[ckittl]

PowerSystemUtils/src/main/scala/edu/ie3/util/osm/OsmModel.scala

Lines 37 to 49 in 05630b8

	/** Convenience method to extract buildings from a list of ways via their tags
	*
	* @param ways
	* the ways to extract from
	* @param specificTagValues
	* only match values within the Set when given otherwise match all
	*/
	def extractBuildings(
	ways: List[Way],
	specificTagValues: Option[Set[String]] = None
	): List[ClosedWay] = {
	extractClosedWays(ways, KeyUtils.BUILDING, specificTagValues)
	}

Buildings can also be modeled as relations (cf. https://www.openstreetmap.org/relation/1401747 or https://www.openstreetmap.org/relation/5490584)

Please add an equivalent method for that.