Add Save() method

[dbgjerez]

No description provided.

[ostafen]

Hi, @dbgjerez, thanks for the PR. I highlighted some adjustments to do before merging.
In particular, Save() can be implemented only using existing functions provided by the StorageEngine. Tests need to be revised, also.

EDIT: I also changed the title of the PR, because it was to generic ;=)

[dbgjerez]

Totally agree with you @ostafen, I have modified the PR, I understand better this code thanks of you.

[ostafen]

Hi, @dbgjerez, sorry for the delay. I requested you some minor changes

[dbgjerez]

Sure bro, I have done both changes. I think that really is better, like you said.

[ostafen]

The implementation of the Save() functions looks good now.
Checks inside TestSaveDocument() needs a minor revision because actually, by only testing the size of the collection with Count() we can only be sure that some document is being saved, but we cannot be sure if the document is consistent.

Also, since we merged the tests, delete the TestSaveNewDocument() function.
I think also that code will be easier to follow if we use string literals directly instead of defining these variables:

collection := "myCollection"
key := "hello"
updatedValue := "clover-updated!"

Thanks for your patience!

[dbgjerez]

Ok, I have done the change and upload it. Thanks!

[ostafen]

Thank you for this!