make Developer email optional as it is not obligatory and some people don`t want to expose it

core/src/main/contraband-scala/sbt/librarymanagement/Developer.scala

@@ -7,7 +7,7 @@ package sbt.librarymanagement
 final class Developer private (
   val id: String,
   val name: String,
-  val email: String,
+  val email: Option[String],
   val url: java.net.URL) extends Serializable {
   
   
@@ -22,7 +22,7 @@ final class Developer private (
   override def toString: String = {
     "Developer(" + id + ", " + name + ", " + email + ", " + url + ")"
   }
-  private[this] def copy(id: String = id, name: String = name, email: String = email, url: java.net.URL = url): Developer = {
+  private[this] def copy(id: String = id, name: String = name, email: Option[String] = email, url: java.net.URL = url): Developer = {
     new Developer(id, name, email, url)
   }
   def withId(id: String): Developer = {
@@ -31,7 +31,7 @@ final class Developer private (
   def withName(name: String): Developer = {
     copy(name = name)
   }
-  def withEmail(email: String): Developer = {
+  def withEmail(email: Option[String]): Developer = {
     copy(email = email)
   }
   def withUrl(url: java.net.URL): Developer = {
@@ -40,5 +40,5 @@ final class Developer private (
 }
 object Developer {
   
-  def apply(id: String, name: String, email: String, url: java.net.URL): Developer = new Developer(id, name, email, url)
+  def apply(id: String, name: String, email: Option[String], url: java.net.URL): Developer = new Developer(id, name, email, url)
 }

core/src/main/contraband-scala/sbt/librarymanagement/DeveloperFormats.scala

@@ -13,7 +13,7 @@ implicit lazy val DeveloperFormat: JsonFormat[sbt.librarymanagement.Developer] =
       unbuilder.beginObject(js)
       val id = unbuilder.readField[String]("id")
       val name = unbuilder.readField[String]("name")
-      val email = unbuilder.readField[String]("email")
+      val email = unbuilder.readField[Option[String]]("email")
       val url = unbuilder.readField[java.net.URL]("url")
       unbuilder.endObject()
       sbt.librarymanagement.Developer(id, name, email, url)

core/src/main/contraband/librarymanagement.json

@@ -328,10 +328,10 @@
       "target": "Scala",
       "type": "record",
       "fields": [
-        { "name": "id",    "type": "String"       },
-        { "name": "name",  "type": "String"       },
-        { "name": "email", "type": "String"       },
-        { "name": "url",   "type": "java.net.URL" }
+        { "name": "id",    "type": "String"         },
+        { "name": "name",  "type": "String"         },
+        { "name": "email", "type": "Option[String]" },
+        { "name": "url",   "type": "java.net.URL"   }
       ]
     },
     {

ivy/src/main/scala/sbt/internal/librarymanagement/MakePom.scala

@@ -206,8 +206,13 @@ class MakePom(val log: Logger) {
             <developer>
               <id>{ developer.id }</id>
               <name>{ developer.name }</name>
-              <email>{ developer.email }</email>
               <url>{ developer.url }</url>
+              {
+                developer.email match {
+                  case Some(e)=> <email>{ e }</email>
+                  case _   => NodeSeq.Empty
+                }
+              }
             </developer>
           }
         }