Support DB2.
Note that this will need single-datasource mode for now. To avoid using single-datasource mode (to be able to use XA) you would have to add the native libdb2jcct2.so/libdb2jcct2.dylib library which hasn't been tested.
The support only includes non-optimized versions of the ACL and path checks, so is not suitable for applications that have a large number of documents or that are using non-Administrator users.
Further work to be done in another ticket TBA depending on resources.