Rsdev 326 backend time validation

[rs-fraser]

This PR adds a new subclass of ExtraField so that we can apply validation specific to time formats. Previously any time fields were treated purely as text and allowed any values.

related rspace-web PR: rspace-os/rspace-web#88

[mKowalski256]

Hmm, what this PR is doing it's actually adding a new type of ExtraField, while I think the goal of the RSDEV-326 ticket was to add validation to existing InventoryTimeField and InventoryDateField which are extensions of SampleField.

ExtraFields (named 'Custom Fields' in the UI) are a functionality where to any individual inventory item (sample/subsample/container) user can add any number of additional fields to store arbitrary more data. Extra fields (custom fields) have just two types: TEXT and NUMBER, and while user can store data/time in ExtraTextField, there is no validation needed.

Extra Fields / Custom Fields in the UI:

Now SampleFields, even though I see are named 'Custom Fields' in the UI, are something specific to Samples and Sample Templates. When creating a Sample Template user can say this template will have a number of Custom Fields that are for specific data type: choice/date/number/time/uri/text/etc. These types are only available for selection when editing a Sample Template, and are only available for filling the data when using the Sample that is based on Sample Template.

Sample Fields / Custom Fields in the UI:

I hope that's clearer now, the validation code and test from this PR is probably reusable, but should end up in/around the existing InventoryTimeField class, rather than in new subclass of ExtraField.

[mKowalski256]

Looks good to me, adding a time field to ComplexSampleTemplate is a good improvement, and I can no longer use API to create sample with incorrect date/time fields: