Compiler warnings

[dennisvang]

Many warnings appear during compilation.

This has been the case for years already, but now I think it's time to clean things up.

For example, compiling v1.22.0 (java 21):

[...]
[WARNING] Unknown file extension: /home/djvangerwen/Documents/repos/fdp/CITATION.cff
[WARNING] Unable to find a comment style definition for some files. You may want to add a custom mapping for the relevant file extensions.
[...]
[WARNING] /home/djvangerwen/Documents/repos/fdp/src/main/java/org/fairdatateam/fairdatapoint/api/dto/search/SearchFilterItemDTO.java:[40,21] @Builder will ignore the initializing expression entirely. If you want the initializing expression to serve as default, add @Builder.Default. If it is not supposed to be settable during building, make the field final.
[WARNING] /home/djvangerwen/Documents/repos/fdp/src/main/java/org/fairdatateam/fairdatapoint/entity/resource/ResourceDefinition.java:[55,26] @Builder will ignore the initializing expression entirely. If you want the initializing expression to serve as default, add @Builder.Default. If it is not supposed to be settable during building, make the field final.
[WARNING] /home/djvangerwen/Documents/repos/fdp/src/main/java/org/fairdatateam/fairdatapoint/entity/resource/ResourceDefinition.java:[57,43] @Builder will ignore the initializing expression entirely. If you want the initializing expression to serve as default, add @Builder.Default. If it is not supposed to be settable during building, make the field final.
[WARNING] /home/djvangerwen/Documents/repos/fdp/src/main/java/org/fairdatateam/fairdatapoint/entity/resource/ResourceDefinition.java:[59,42] @Builder will ignore the initializing expression entirely. If you want the initializing expression to serve as default, add @Builder.Default. If it is not supposed to be settable during building, make the field final.
[WARNING] /home/djvangerwen/Documents/repos/fdp/src/main/java/org/fairdatateam/fairdatapoint/entity/index/entry/IndexEntry.java:[50,29] @Builder will ignore the initializing expression entirely. If you want the initializing expression to serve as default, add @Builder.Default. If it is not supposed to be settable during building, make the field final.
[WARNING] /home/djvangerwen/Documents/repos/fdp/src/main/java/org/fairdatateam/fairdatapoint/entity/index/entry/IndexEntry.java:[52,30] @Builder will ignore the initializing expression entirely. If you want the initializing expression to serve as default, add @Builder.Default. If it is not supposed to be settable during building, make the field final.
[WARNING] /home/djvangerwen/Documents/repos/fdp/src/main/java/org/fairdatateam/fairdatapoint/entity/schema/MetadataSchema.java:[75,25] @Builder will ignore the initializing expression entirely. If you want the initializing expression to serve as default, add @Builder.Default. If it is not supposed to be settable during building, make the field final.
[WARNING] /home/djvangerwen/Documents/repos/fdp/src/main/java/org/fairdatateam/fairdatapoint/entity/schema/MetadataSchema.java:[78,26] @Builder will ignore the initializing expression entirely. If you want the initializing expression to serve as default, add @Builder.Default. If it is not supposed to be settable during building, make the field final.
[...]
[WARNING] /home/djvangerwen/Documents/repos/fdp/src/test/java/org/fairdatateam/fairdatapoint/service/index/harvester/HarvesterServiceTest.java:[129,47] <T>ResponseEntity(T,org.springframework.util.MultiValueMap<java.lang.String,java.lang.String>,org.springframework.http.HttpStatusCode) in org.springframework.http.ResponseEntity has been deprecated and marked for removal
[...]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  8.940 s
[INFO] Finished at: 2026-08-10T17:11:52+02:00
[INFO] ------------------------------------------------------------------------