fix: zero decimal bug

[nae701]

Description

Fixes issue #5282, where there was a bug that would not allow the insertion of valid decimals if they were equal to 0. This was due to an edge case in how BigDecimal calculates precision for zero decimal values. This patch adds a condition to check for zero decimal values and calculates their precision correctly.

Testing done

A unit test checking if the server allows the insertion of valid zero decimals was added to the rest-query-validation-tests folder.

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[ghost]

It looks like @nae701 hasn't signed our Contributor License Agreement, yet.

The purpose of a CLA is to ensure that the guardian of a project's outputs has the necessary ownership or grants of rights over all contributions to allow them to distribute under the chosen licence.
Wikipedia

You can read and sign our full Contributor License Agreement here.

Once you've signed reply with [clabot:check] to prove it.

Appreciation of efforts,

clabot

[agavra]

Thanks again @nae701 - crushing it :D left mostly minor comments

[agavra]

LGTM! Thanks @nae701