fix issue #7326

Motivation:

the nested groups are not included by Frontend:

wget -q --no-check-certificate https://dcacheweb-kit.gridka.de:3880/api/v1/poolgroups -O - | jq '.[] | select(.name == "all-belle-pools")'
{
  "name": "all-belle-pools"
}

Modification:

add a way do get poolGroups from poolSelectionUnit

Result:

Nested groups are  shown

[
{"name":"alias-pools",
"nestedPoolGroups":["qos-disk"]
},
{
"name":"alias-pools1",
"nestedPoolGroups":["alias-pools2","qos-disk","resgroup"]
},
{
"name":"alias-pools2"
},
{
"name":"default"
},
{
"name":"qos-disk",
"pools":["pool_res1","pool_res2","pool_res3"]
},
{
"name":"resgroup",
"links":["resilient-link"],
"pools":["pool_res1","pool_res2","pool_res3"],
"nestedPoolGroups":["alias-pools2"]
}
]

Target: master
Request: 9.0
Request: 8.2
Request: 8.1
Acted-by: Tigran Mkrtchyan
Fixes: #7326
Requires-notes: yes
Requires-book:

modules/dcache-frontend/src/main/java/org/dcache/restful/providers/selection/PoolGroup.java

@@ -62,6 +62,7 @@ LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 import diskCacheV111.poolManager.PoolSelectionUnit;
 import diskCacheV111.poolManager.PoolSelectionUnit.SelectionLink;
 import diskCacheV111.poolManager.PoolSelectionUnit.SelectionPool;
+import diskCacheV111.poolManager.PoolSelectionUnit.SelectionPoolGroup;
 import io.swagger.annotations.ApiModel;
 import io.swagger.annotations.ApiModelProperty;
 import java.util.Comparator;
@@ -76,8 +77,13 @@ public final class PoolGroup extends SelectionTypeWithLinks {
     @ApiModelProperty("The pools that are a member of this poolgroup.")
     private final List<String> pools;
 
+    @ApiModelProperty("The Nested poolGroups that are a member of this poolgroup.")
+    private final List<String> nestedPoolGroups;
+
     public PoolGroup() {
         this.pools = null;
+        this.nestedPoolGroups = null;
+
     }
 
     public PoolGroup(String group, PoolSelectionUnit psu) {
@@ -87,12 +93,20 @@ public PoolGroup(String group, PoolSelectionUnit psu) {
               .sorted(Comparator.comparing(SelectionPool::getName))
               .map(SelectionPool::getName)
               .collect(Collectors.toList());
+
+        nestedPoolGroups = psu.getPoolGroupByName(name).getPoolGroups().stream()
+              .map((SelectionPoolGroup::getName))
+              .collect(Collectors.toList());
     }
 
     public List<String> getPools() {
         return pools;
     }
 
+    public List<String> getNestedPoolGroups() {
+        return nestedPoolGroups;
+    }
+
     @Override
     protected List<String> extractLinks(PoolSelectionUnit psu) {
         return psu.getLinksPointingToPoolGroup(name)

modules/dcache-resilience/src/test/java/org/dcache/resilience/TestSelectionUnit.java

@@ -158,6 +158,11 @@ public Map<String, SelectionPool> getPools() {
         return psu.getPools();
     }
 
+    @Override
+    public SelectionPoolGroup getPoolGroupByName(String poolGroup) throws NoSuchElementException {
+        return psu.getPoolGroupByName(poolGroup);
+    }
+
     @Override
     public Collection<SelectionPool> getPoolsByPoolGroup(String poolGroup)
           throws NoSuchElementException {

modules/dcache/src/main/java/diskCacheV111/poolManager/PGroup.java

@@ -47,6 +47,10 @@ public List<Pool> getPools() {
         return allPools;
     }
 
+    @Override
+    public List<PGroup> getPoolGroups() {
+        return _pgroupList;
+    }
 
     // check whatever there is a pool group that exist in there reference list
     // IOW, A ->  B -> C ; C -> A not allowed.

modules/dcache/src/main/java/diskCacheV111/poolManager/PoolSelectionUnit.java

@@ -196,6 +196,7 @@ interface SelectionPoolGroup extends SelectionEntity {
         boolean isResilient();
 
         List<? extends SelectionPool> getPools();
+        List<? extends SelectionPoolGroup> getPoolGroups();
     }
 
     interface SelectionLinkGroup extends SelectionEntity {
@@ -300,5 +301,7 @@ Collection<SelectionLink> getLinksPointingToPoolGroup(String poolGroup)
 
     Map<String, SelectionUnitGroup> getUnitGroups();
 
+    SelectionPoolGroup getPoolGroupByName(String poolGroup);
+
     boolean isEnabledRegex();
 }

modules/dcache/src/main/java/diskCacheV111/poolManager/PoolSelectionUnitV2.java

@@ -2544,6 +2544,18 @@ public LinkGroup getLinkGroupByName(String linkGroupName) {
         return linkGroup;
     }
 
+    @Override
+    public PGroup getPoolGroupByName(String pgroup) {
+        PGroup poolGroup = null;
+        rlock();
+        try {
+            poolGroup = _pGroups.get(pgroup);
+        } finally {
+            runlock();
+        }
+        return poolGroup;
+    }
+
     @Override
     public Collection<SelectionPoolGroup> getPoolGroupsOfPool(String poolName) {
         rlock();