feat: convert string commands to enum

[jmarkerink]

I hope you are appreciating this refactoring with strong typing.

I have modeled the supported/implemented commands in a enumeration and wrapped it in a value object so we can retrieve the original query command string because of the case insensitivity.

Some benefits:

• compile-time safety - typos are caught at compile time
• documentation - enum serves as documentation of all supported commands
• performance - single toLowerCase() with HashMap lookup

[bwaldvogel]

Could you please cleanup and squash the commits of this PR? (eg. using git rebase --interactive)

[bwaldvogel]

Can you elaborate on the purpose of this class? It’s not very unintuitive IMO. Why is it okay that equals/hashCode takes only the command field?

Why do we need the static constructors?

Is queryValue a good field name?

[jmarkerink]

Could you please cleanup and squash the commits of this PR? (eg. using git rebase --interactive)

I have cleanup a bit. Thanks, learned something from this exercise 🤓

Because the command string is case-insensitive in some cases I wrapped it in this value object so we can access the received command too and parsing can be done in a few places.

To exclude the case sensitivity I left out the received query command string in the equals / hashCode.

Static constructor in this case, is a style I prefer, but I can changed this to you preference.

How do you want proceed with this PR, do you think this can be a good addition if we amend your comments?

Shall I

• Remove the static constructors and rename queryValue to e.g. queryCommand or
• Drop the value object DatabaseCommand and change e.g. the code, from

public Document handleCommand(Channel channel, String databaseName, DatabaseCommand command, Document query) {
        return switch (command.getCommand()) {

To

public Document handleCommand(Channel channel, String databaseName, String command, Document query) {
       return switch (Command.parseString(command)) {

Please share you thoughts.