fix the reported CRS identifier when the CRS84 alias URI is requested

xtraplatform-crs/src/main/java/de/ii/xtraplatform/crs/domain/EpsgCrs.java

@@ -89,6 +89,17 @@ default Force getForceAxisOrder() {
     return Force.NONE;
   }
 
+  /**
+   * Optional CRS identifier (URI) used to reference this CRS, e.g., the alias
+   * "http://www.opengis.net/def/crs/OGC/0/CRS84" for CRS84. If present, {@code toUriString()}
+   * returns this value so that responses echo the identifier used in the request. Auxiliary, i.e.,
+   * excluded from {@code equals()}/{@code hashCode()}: instances differing only in this attribute
+   * represent the same CRS.
+   */
+  @JsonIgnore
+  @Value.Auxiliary
+  Optional<String> getUriOverride();
+
   @JsonIgnore
   @Value.Lazy
   default boolean isCompoundCrs() {
@@ -130,6 +141,9 @@ default List<String> toUrnStrings() {
   @JsonIgnore
   @Value.Lazy
   default String toUriString() {
+    if (getUriOverride().isPresent()) {
+      return getUriOverride().get();
+    }
     if (Objects.equals(this, OgcCrs.CRS84)) {
       return OgcCrs.CRS84_URI;
     }
@@ -139,12 +153,18 @@ default String toUriString() {
     return String.format("http://www.opengis.net/def/crs/EPSG/0/%d", getCode());
   }
 
+  /**
+   * Returns all registered URIs of this CRS: the canonical URI plus, in the case of CRS84, the
+   * "OGC/0/CRS84" alias URI. Unlike {@code toUriStrings()}, the list does not decompose a compound
+   * CRS into its components, it lists the identifiers of this CRS.
+   */
   @JsonIgnore
   @Value.Lazy
-  default Optional<String> toAlternativeUriString() {
-    return Objects.equals(this, OgcCrs.CRS84)
-        ? Optional.of(OgcCrs.CRS84_URI_NEW)
-        : Optional.empty();
+  default List<String> allUris() {
+    if (Objects.equals(this, OgcCrs.CRS84)) {
+      return List.of(OgcCrs.CRS84_URI, OgcCrs.CRS84_URI_NEW);
+    }
+    return List.of(toUriString());
   }
 
   @JsonIgnore

xtraplatform-crs/src/main/java/de/ii/xtraplatform/crs/domain/OgcCrs.java

@@ -20,14 +20,21 @@ public interface OgcCrs {
   String CRS84_URI_NEW = "http://www.opengis.net/def/crs/OGC/0/CRS84";
   String CRS84_CURIE = "OGC:CRS84";
 
+  /**
+   * The same CRS as {@link #CRS84} ({@code equals()} is {@code true}), but {@code toUriString()}
+   * returns the "OGC/0/CRS84" alias URI instead of the "OGC/1.3/CRS84" URI.
+   */
+  EpsgCrs CRS84_OGC0 =
+      new ImmutableEpsgCrs.Builder().from(CRS84).uriOverride(CRS84_URI_NEW).build();
+
   EpsgCrs CRS84h = EpsgCrs.of(4979, Force.LON_LAT);
 
   String CRS84h_URI = "http://www.opengis.net/def/crs/OGC/0/CRS84h";
   String CRS84h_CURIE = "OGC:CRS84h";
 
   static Optional<EpsgCrs> fromString(String prefixedCode) {
     if (Objects.equals(prefixedCode, CRS84_URI_NEW)) {
-      return Optional.of(CRS84);
+      return Optional.of(CRS84_OGC0);
     }
     if (Objects.equals(prefixedCode, CRS84_URI)) {
       return Optional.of(CRS84);

xtraplatform-crs/src/test/groovy/de/ii/xtraplatform/crs/infra/EpsgCrsSpec.groovy

@@ -43,6 +43,21 @@ class EpsgCrsSpec extends Specification {
 
     }
 
+    def 'fromString - crs84 alias'() {
+        when:
+        def crs = EpsgCrs.fromString(OgcCrs.CRS84_URI_NEW)
+
+        then:
+        crs.code == 4326
+        crs.forceAxisOrder == EpsgCrs.Force.LON_LAT
+        crs == OgcCrs.CRS84
+        crs.hashCode() == OgcCrs.CRS84.hashCode()
+        crs.toUriString() == OgcCrs.CRS84_URI_NEW
+        crs.toUrnString() == "urn:ogc:def:crs:OGC::4326"
+        crs.toSafeCurie() == OgcCrs.CRS84_CURIE
+
+    }
+
     def 'fromString - crs84h'() {
         when:
         def crs = EpsgCrs.fromString(OgcCrs.CRS84h_URI)
@@ -93,10 +108,23 @@ class EpsgCrsSpec extends Specification {
         crs.toUriString() == uri
 
         where:
-        crs               | uri
-        EpsgCrs.of(25832) | "http://www.opengis.net/def/crs/EPSG/0/25832"
-        OgcCrs.CRS84      | OgcCrs.CRS84_URI
-        OgcCrs.CRS84h     | OgcCrs.CRS84h_URI
+        crs                | uri
+        EpsgCrs.of(25832)  | "http://www.opengis.net/def/crs/EPSG/0/25832"
+        OgcCrs.CRS84       | OgcCrs.CRS84_URI
+        OgcCrs.CRS84_OGC0  | OgcCrs.CRS84_URI_NEW
+        OgcCrs.CRS84h      | OgcCrs.CRS84h_URI
+    }
+
+    def 'allUris'() {
+        expect:
+        crs.allUris() == uris
+
+        where:
+        crs                | uris
+        EpsgCrs.of(25832)  | ["http://www.opengis.net/def/crs/EPSG/0/25832"]
+        OgcCrs.CRS84       | [OgcCrs.CRS84_URI, OgcCrs.CRS84_URI_NEW]
+        OgcCrs.CRS84_OGC0  | [OgcCrs.CRS84_URI, OgcCrs.CRS84_URI_NEW]
+        OgcCrs.CRS84h      | [OgcCrs.CRS84h_URI]
     }
 
     def 'CoordinateTupleWithPrecision - uri'() {