Add Country entity

core/src/main/java/cz/muni/fi/pa165/core/data/domain/Country.java

+package cz.muni.fi.pa165.core.data.domain;
+
+import cz.muni.fi.pa165.core.data.domain.common.DomainEntity;
+import jakarta.persistence.Column;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Table;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import lombok.NonNull;
+
+import java.util.Objects;
+
+@Entity
+@Table(name = "countries")
+@Data
+@NoArgsConstructor
+public class Country extends DomainEntity {
+
+    @Column(nullable = false, unique = true)
+    private @NonNull String name;
+
+    // TODO: Add relationship Country - City
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (!(o instanceof Country country)) {
+            return false;
+        }
+        return getName().equals(country.getName());
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(getName());
+    }
+}