F grpc select

Summary

1. Implementation of SELECT queries for the GRPC API (https://gitlab.indiscale.com/caosdb/customers/leibniz-zmt/management/-/issues/110)
2. (Re)fix of an undead server bug (https://gitlab.com/caosdb/caosdb-server/-/issues/136)
3. Correction of a wrong implementation of FIND queries which was not recognized before. This will lead to the necessity to fix https://gitlab.indiscale.com/caosdb/customers/cfaed/complexitywiki/-/issues/1

Focus

Most of the code related to 1. is located in src/main/java/org/caosdb/server/grpc/EntityTransactionServiceImpl.java and src/main/java/org/caosdb/server/grpc/CaosDBToGrpcConverters.java.

Everything else is mostly general refactoring or fixing the mentioned issues 2. and 3.

Test Environment

No manual testing necessary.

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• All automated tests pass
• Reference related issues
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  • Intent of new code
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• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
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src/main/java/org/caosdb/server/datatype/BooleanDatatype.java

@@ -32,6 +32,8 @@ public class BooleanDatatype extends AbstractDatatype {
   public SingleValue parseValue(final Object value) throws Message {
     if (value instanceof BooleanValue) {
       return (SingleValue) value;
+    } else if (value instanceof CollectionValue) {
+      throw ServerMessages.DATA_TYPE_DOES_NOT_ACCEPT_COLLECTION_VALUES;
     } else if (value instanceof SingleValue) {
       return parse(((SingleValue) value).toDatabaseString());
     } else {