replace OncePerRequestFilter subclass by a custom micrometer ObservationFilter implementation

following the examples from the spring-boot docs
https://docs.spring.io/spring-framework/reference/integration/observability.html#observability.config.conventions

Author: dennisvang

src/main/java/nl/dtls/fairdatapoint/api/filter/RequestMetricsFilter.java

@@ -0,0 +1,57 @@
+/**
+ * The MIT License
+ * Copyright © 2017 DTL
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package nl.dtls.fairdatapoint.api.filter;
+
+import io.micrometer.common.KeyValue;
+import io.micrometer.observation.Observation;
+import io.micrometer.observation.ObservationFilter;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.http.server.observation.ServerRequestObservationContext;
+import org.springframework.stereotype.Component;
+
+import java.util.Optional;
+
+@Slf4j
+@Component
+public class RequestObservationFilter implements ObservationFilter {
+
+    /**
+     * Replaces the actuator metrics http.server.requests default `uri` path pattern values with full paths.
+     * @param context Micrometer Observation.Context
+     * @return modified context
+     */
+    @Override
+    public Observation.Context map(Observation.Context context) {
+        if (context instanceof ServerRequestObservationContext serverContext) {
+            log.debug("Using customized micrometer observation context");
+            final Optional<String> requestURI = Optional.ofNullable(serverContext.getCarrier().getRequestURI());
+            // Replace the default URI path pattern (e.g. `/catalog/{id}`) with the full URI path (e.g. `/catalog/123`).
+            // This is high-cardinality data, but we add it as low-cardinality to make sure it shows up in the metrics.
+            // Beware, this could lead to memory issues in case of excessive number of URIs.
+            // See micrometer docs for more info.
+            context.addLowCardinalityKeyValue(KeyValue.of("uri", requestURI.orElse("")));
+        }
+        return context;
+    }
+}