Write data value

[andrewwkoerner]

Description

Allow support for writing ua::DataValue to a server.

Testing details

Tested and confirmed OPC-UA Server example writes to a variable node with a ua::DataValue in example code.
Viewed data with a separate OPC-UA client.

Confirmed pre-commit output.

akoerner@xyz open62541 % just pre-commit
pre-commit run --all-files
check for case conflicts.................................................Passed
check json...........................................(no files to check)Skipped
check for merge conflicts................................................Passed
check for broken symlinks............................(no files to check)Skipped
check toml...............................................................Passed
check xml............................................(no files to check)Skipped
check yaml...............................................................Passed
detect destroyed symlinks................................................Passed
detect private key.......................................................Passed
fix end of files.........................................................Passed
fix utf-8 byte order marker..............................................Passed
forbid new submodules................................(no files to check)Skipped
mixed line ending........................................................Passed
trim trailing whitespace.................................................Passed
markdownlint-cli2........................................................Passed
codespell................................................................Passed
Validate GitHub Actions..............................(no files to check)Skipped
Validate GitHub Workflows................................................Passed
taplo-format.............................................................Passed
taplo-lint...............................................................Passed
prettier.................................................................Passed
fmt......................................................................Passed
clippy --all-features....................................................Passed
clippy --no-default-features.............................................Passed
cargo-doc................................................................Passed

[sgoll]

@andrewwkoerner Thank you! I made some minor adjustments of related aspects of the existing code, but this looks good to go.

[sgoll]

Motivation for this related change: In #151 we added timestamp attributes to DataValue without taking into account that we have to retrieve them here first.

We may revisit the default action of always returning (retrieving) both timestamps in the future.