feat: History entries can also be made about other authenticated

subjects.

src/main/java/com/sitepark/ies/contentrepository/core/domain/entity/HistoryEntry.java

@@ -1,11 +1,13 @@
 package com.sitepark.ies.contentrepository.core.domain.entity;
 
 import java.io.Serializable;
+import java.util.Optional;
 
 public final class HistoryEntry implements Serializable {
 
 	private final long entity;
-	private final long user;
+	private final String initiator;
+	private final Long user;
 	private final long timestamp;
 	private final HistoryEntryType type;
 	private final String comment;
@@ -14,6 +16,7 @@ public final class HistoryEntry implements Serializable {
 
 	private HistoryEntry(Builder builder) {
 		this.entity = builder.entity;
+		this.initiator = builder.initiator;
 		this.user = builder.user;
 		this.timestamp = builder.timestamp;
 		this.type = builder.type;
@@ -24,8 +27,19 @@ public long getEntity() {
 		return entity;
 	}
 
-	public long getUser() {
-		return user;
+	/**
+	 * The initiator can be a user of a system-service or other subjects who
+	 * could authenticate themselves to work with the system.
+	 */
+	public String getInitiator() {
+		return initiator;
+	}
+
+	/**
+	 * If the initiator is a user of the IES, this returns the ID of the user.
+	 */
+	public Optional<Long> getUser() {
+		return Optional.ofNullable(this.user);
 	}
 
 	public long getTimestamp() {
@@ -51,7 +65,8 @@ public Builder toBuilder() {
 	public static class Builder {
 
 		private long entity;
-		private long user;
+		private String initiator;
+		private Long user;
 		private long timestamp;
 		private HistoryEntryType type;
 		private String comment;
@@ -60,6 +75,7 @@ private Builder() { }
 
 		private Builder(HistoryEntry historyEntry) {
 			this.entity = historyEntry.entity;
+			this.initiator = historyEntry.initiator;
 			this.user = historyEntry.user;
 			this.timestamp = historyEntry.timestamp;
 			this.type = historyEntry.type;
@@ -71,7 +87,13 @@ public Builder entity(long entity) {
 			return this;
 		}
 
-		public Builder user(long user) {
+		public Builder initiator(String initiator) {
+			assert initiator != null : "initiator is null";
+			this.initiator = initiator;
+			return this;
+		}
+
+		public Builder user(Long user) {
 			this.user = user;
 			return this;
 		}
@@ -83,13 +105,13 @@ public Builder timestamp(long timestamp) {
 		}
 
 		public Builder type(HistoryEntryType type) {
-			assert type != null;
+			assert type != null : "type is null";
 			this.type = type;
 			return this;
 		}
 
 		public Builder comment(String comment) {
-			assert comment != null;
+			assert comment != null : "comment is null";
 			this.comment = comment;
 			return this;
 		}