[BUG] check compatibility with latest existdb releases >= 5.4.0

[line-o]

Tests for latest commit are failing!

• https://github.com/eXist-db/expath-crypto-module/runs/4801843371?check_suite_focus=true#step:6:181

With #63 applied the lib does not even compile!

• https://github.com/eXist-db/expath-crypto-module/runs/5135540349?check_suite_focus=true#step:5:1550

[joewiz]

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  2.093 s
[INFO] Finished at: 2022-03-14T15:18:31-04:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile (default-compile) on project expath-crypto-module: Compilation failure
[ERROR] /Users/joe/workspace/expath-crypto-module/src/main/java/org/expath/exist/crypto/digitalSignature/GenerateSignatureFunction.java:[177,117] incompatible types: org.exist.storage.serializers.Serializer cannot be converted to com.evolvedbinary.j8fu.function.ConsumerE<com.evolvedbinary.j8fu.function.ConsumerE<org.exist.storage.serializers.Serializer,java.io.IOException>,java.io.IOException>