Switch error to DocumentTooLargeError

Author: kmahar

Sources/MongoSwift/BSON/BSONDocument.swift

@@ -229,7 +229,7 @@ extension BSONDocument {
             }
         }
         guard success else {
-            throw BSONError.InternalError(
+            throw BSONError.DocumentTooLargeError(
                 message: "Failed to merge \(doc) with \(self). This is likely due to " +
                     "the merged document being too large."
             )

Sources/MongoSwift/BSON/BSONError.swift

@@ -38,6 +38,10 @@ public enum BSONError {
                 "Failed to set value for key \(forKey) to \(value) with" +
                 " BSON type \(value.bsonType): document too large"
         }
+
+        internal init(message: String) {
+            self.message = message
+        }
     }
 }