Adds monster collections.

Android/app/src/main/java/com/majinnaibu/monstercards/models/Collection.java

@@ -0,0 +1,53 @@
+package com.majinnaibu.monstercards.models;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.room.ColumnInfo;
+import androidx.room.Entity;
+import androidx.room.PrimaryKey;
+
+import java.util.Objects;
+import java.util.UUID;
+
+@Entity(tableName = "collections")
+public class Collection {
+
+    @PrimaryKey
+    @NonNull
+    public UUID id;
+
+    @NonNull
+    @ColumnInfo(defaultValue = "")
+    public String name;
+
+    @NonNull
+    @ColumnInfo(defaultValue = "")
+    public String description;
+
+    public Collection() {
+        this.id = UUID.randomUUID();
+        this.name = "";
+        this.description = "";
+    }
+
+    public Collection(@NonNull String name, @NonNull String description) {
+        this.id = UUID.randomUUID();
+        this.name = name;
+        this.description = description;
+    }
+
+    @Override
+    public boolean equals(@Nullable Object obj) {
+        if (this == obj) return true;
+        if (obj == null || getClass() != obj.getClass()) return false;
+        Collection that = (Collection) obj;
+        return Objects.equals(id, that.id) &&
+                Objects.equals(name, that.name) &&
+                Objects.equals(description, that.description);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id, name, description);
+    }
+}

Android/app/src/main/java/com/majinnaibu/monstercards/models/CollectionMonster.java

@@ -0,0 +1,60 @@
+package com.majinnaibu.monstercards.models;
+
+import androidx.annotation.NonNull;
+import androidx.room.ColumnInfo;
+import androidx.room.Entity;
+import androidx.room.ForeignKey;
+import androidx.room.Index;
+import androidx.room.PrimaryKey;
+
+import java.util.UUID;
+
+@Entity(
+        tableName = "collection_monsters",
+        foreignKeys = {
+                @ForeignKey(
+                        entity = Collection.class,
+                        parentColumns = "id",
+                        childColumns = "collection_id",
+                        onDelete = ForeignKey.CASCADE
+                ),
+                @ForeignKey(
+                        entity = Monster.class,
+                        parentColumns = "id",
+                        childColumns = "monster_id",
+                        onDelete = ForeignKey.CASCADE
+                )
+        },
+        indices = {
+                @Index(value = {"collection_id"}),
+                @Index(value = {"monster_id"})
+        }
+)
+public class CollectionMonster {
+
+    @PrimaryKey(autoGenerate = true)
+    public long id;
+
+    @NonNull
+    @ColumnInfo(name = "collection_id")
+    public UUID collectionId;
+
+    @NonNull
+    @ColumnInfo(name = "monster_id")
+    public UUID monsterId;
+
+    @ColumnInfo(name = "ordinal", defaultValue = "0")
+    public int ordinal;
+
+    public CollectionMonster() {
+        this.collectionId = UUID.fromString("00000000-0000-0000-0000-000000000000");
+        this.monsterId = UUID.fromString("00000000-0000-0000-0000-000000000000");
+        this.ordinal = 0;
+    }
+
+    public CollectionMonster(@NonNull UUID collectionId, @NonNull UUID monsterId, int ordinal) {
+        this.collectionId = collectionId;
+        this.monsterId = monsterId;
+        this.ordinal = ordinal;
+    }
+}

Android/app/src/main/java/com/majinnaibu/monstercards/models/CollectionWithCount.java

@@ -0,0 +1,20 @@
+package com.majinnaibu.monstercards.models;
+
+import androidx.room.Embedded;
+
+public class CollectionWithCount {
+    @Embedded
+    public Collection collection;
+
+    public int monsterCount;
+
+    public CollectionWithCount() {
+        this.collection = new Collection();
+        this.monsterCount = 0;
+    }
+
+    public CollectionWithCount(Collection collection, int monsterCount) {
+        this.collection = collection;
+        this.monsterCount = monsterCount;
+    }
+}