Added group edition APIs.

Still incomplete, still WIP, but it’s a start.

src/group.cr

@@ -1,10 +1,10 @@
 require "csv"
 
 class Passwd::Group
-	getter name            : String
-	getter password_hash   : String
-	getter gid             : Int32
-	getter users           = Array(String).new
+	property name            : String
+	property password_hash   : String
+	property gid             : Int32
+	property users           = Array(String).new
 
 	def initialize(@name, @password_hash, @gid, @users = [] of String)
 	end

src/passwd.cr

@@ -87,6 +87,12 @@ class Passwd
 		end
 	end
 
+	def each_group(&block)
+		group_as_array.each do |line|
+			yield Passwd::Group.new line
+		end
+	end
+
 	def get_all_users
 		users = Array(Passwd::User).new
 
@@ -97,6 +103,22 @@ class Passwd
 		users
 	end
 
+	def get_group(&block) : Passwd::Group?
+		each_group do |group|
+			if yield group
+				return group
+			end
+		end
+	end
+
+	def get_group(gid : Int32)
+		get_group &.gid.==(gid)
+	end
+
+	def get_group(name : String)
+		get_group &.name.==(name)
+	end
+
 	def get_all_groups
 		groups = Array(Passwd::Group).new
 
@@ -211,6 +233,20 @@ class Passwd
 		File.write @passwd, new_passwd.join("\n") + "\n"
 	end
 
+	def mod_group(group : ::Passwd::Group)
+		new_group = group_as_array.map do |line|
+			_group = Passwd::Group.new line
+
+			if _group.gid == group.gid
+				group.to_csv
+			else
+				line.join(':')
+			end
+		end
+
+		File.write @group, new_group.join('\n') + '\n'
+	end
+
 	private def safe_rewrite(path : String, body : String)
 		tempfile = File.tempfile(File.basename path)
 		tempfile << body

src/user.cr

@@ -1,18 +1,18 @@
 require "csv"
 
 class Passwd::User
-	getter uid             : Int32
-	getter gid             : Int32
-	getter login           : String
-	getter password_hash   : String
-	getter home            : String = "/"
-	getter shell           : String = "/bin/nologin"
-	getter groups          = Array(String).new
-	getter full_name       : String? = nil
-	getter location        : String? = nil
-	getter office_phone_number : String? = nil
-	getter home_phone_number   : String? = nil
-	getter other_contact   : String? = nil
+	property uid             : Int32
+	property gid             : Int32
+	property login           : String
+	property password_hash   : String
+	property home            : String = "/"
+	property shell           : String = "/bin/nologin"
+	property groups          = Array(String).new
+	property full_name       : String? = nil
+	property location        : String? = nil
+	property office_phone_number : String? = nil
+	property home_phone_number   : String? = nil
+	property other_contact   : String? = nil
 
 	def initialize(
 		@login,