Rename Authorship entity to Edit

As we now have a separate Author entity, which holds information
about an author (the color), the Authorship name became confusing.
Edit seems to be a better name, as the entity saves information
about a change in a note.

Signed-off-by: David Mehren <git@herrmehren.de>

src/revisions/edit.entity.ts

@@ -0,0 +1,61 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import {
+  Column,
+  CreateDateColumn,
+  Entity,
+  ManyToMany,
+  ManyToOne,
+  PrimaryGeneratedColumn,
+  UpdateDateColumn,
+} from 'typeorm';
+import { Author } from '../authors/author.entity';
+import { Revision } from './revision.entity';
+
+/**
+ * The Edit represents a change in the content of a note by a particular {@link Author}
+ */
+@Entity()
+export class Edit {
+  @PrimaryGeneratedColumn('uuid')
+  id: string;
+
+  /**
+   * Revisions this edit appears in
+   */
+  @ManyToMany((_) => Revision, (revision) => revision.edits)
+  revisions: Revision[];
+
+  /**
+   * Author that created the change
+   */
+  @ManyToOne(() => Author, (author) => author.edits)
+  author: Author;
+
+  @Column()
+  startPos: number;
+
+  @Column()
+  endPos: number;
+
+  @CreateDateColumn()
+  createdAt: Date;
+
+  @UpdateDateColumn()
+  updatedAt: Date;
+
+  // eslint-disable-next-line @typescript-eslint/no-empty-function
+  private constructor() {}
+
+  public static create(author: Author, startPos: number, endPos: number) {
+    const newEdit = new Edit();
+    newEdit.author = author;
+    newEdit.startPos = startPos;
+    newEdit.endPos = endPos;
+    return newEdit;
+  }
+}