domain - set some columns to arbitrary length (TEXT type)

In some cases we would need more than the default length for string
(255chars).

As indicated in a comment, this is not portable, but works with
postgresql which is the de-facto standard in geOrchestra ?
Rapidly checking, it looks like Oracle also supports it.

Tests: runtime tested.

domain/src/main/java/org/fao/geonet/domain/Group.java

@@ -31,28 +31,8 @@
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
-import javax.persistence.Access;
-import javax.persistence.AccessType;
-import javax.persistence.Cacheable;
-import javax.persistence.CascadeType;
-import javax.persistence.CollectionTable;
-import javax.persistence.Column;
-import javax.persistence.Convert;
-import javax.persistence.ElementCollection;
-import javax.persistence.Entity;
-import javax.persistence.EntityListeners;
-import javax.persistence.FetchType;
-import javax.persistence.GeneratedValue;
-import javax.persistence.GenerationType;
-import javax.persistence.Id;
-import javax.persistence.JoinColumn;
-import javax.persistence.JoinTable;
-import javax.persistence.ManyToMany;
-import javax.persistence.ManyToOne;
-import javax.persistence.MapKeyColumn;
-import javax.persistence.SequenceGenerator;
-import javax.persistence.Table;
-import javax.persistence.Transient;
+import javax.persistence.*;
+
 import org.fao.geonet.domain.converter.BooleanToYNConverter;
 
 import org.fao.geonet.entitylistener.GroupEntityListenerManager;
@@ -141,7 +121,7 @@ public Group setName(String name) {
      *
      * @return the description.
      */
-    @Column(length = 255)
+    @Column(columnDefinition = "TEXT")
     public String getDescription() {
         return _description;
     }
@@ -245,6 +225,7 @@ public boolean isReserved() {
      * @return the filename of the logo or null if there is no logo associated with this group.
      */
     @Nullable
+    @Column(columnDefinition = "TEXT")
     public String getLogo() {
         return logo;
     }

domain/src/main/java/org/fao/geonet/domain/external/ExternalGroupLink.java

@@ -20,12 +20,7 @@
 
 import java.util.Objects;
 
-import javax.persistence.Access;
-import javax.persistence.AccessType;
-import javax.persistence.Entity;
-import javax.persistence.Id;
-import javax.persistence.OneToOne;
-import javax.persistence.Table;
+import javax.persistence.*;
 
 import org.fao.geonet.domain.Group;
 
@@ -55,6 +50,7 @@ public enum GroupSyncMode {
     private String externalId;
     private GroupSyncMode origin;
     private String name;
+
     private String description;
     private String linkage;
     private String lastUpdated;
@@ -108,6 +104,12 @@ public ExternalGroupLink setName(String name) {
         return this;
     }
 
+    /**
+     * Note: this is not portable, as the TEXT definition does not
+     * exist on all DBMS. But considering geOrchestra, we are supposed
+     * to rely on a PostGreSQL server.
+     */
+    @Column(columnDefinition = "TEXT")
     public String getDescription() {
         return description;
     }