Only serve static assets out of /assets

This avoids Spring doing resource resolution for every link on page
which seems to cost us over 100ms on some pages in some environments.

See: spring-projects/spring-framework#27538

ui/resources/application.properties

@@ -50,6 +50,8 @@ server.servlet.context-path=${CONTEXT_PATH:/}
 spring.web.resources.cache.cachecontrol.max-age=1d
 spring.web.resources.chain.strategy.content.enabled=true
 spring.web.resources.chain.strategy.content.paths=/**
+spring.web.resources.static-locations=classpath:/static/assets/
+spring.mvc.static-path-pattern=/assets/**
 # Obey X-Forwarded-* headers
 server.forward-headers-strategy=NATIVE
 server.tomcat.remoteip.remote-ip-header=X-Forwarded-For

ui/resources/templates/MarcExport.html

@@ -18,7 +18,7 @@
 <script th:src="@{/webjars/webshim/1.15.8/dev/polyfiller.js}" defer></script>
 <script th:src="@{/webjars/datatables/1.10.21/js/jquery.dataTables.min.js}" defer></script>
 <script th:src="@{/webjars/datatables/1.10.21/js/dataTables.bootstrap4.min.js}" defer></script>
-<script th:src="@{/marcexport/MarcExport.js}" defer></script>
+<script th:src="@{/assets/MarcExport.js}" defer></script>
 
 <style>
     form textarea {