feat: add isoDate schema to zod and ajv

[mrnagydavid]

Before anything: Ajv is one of the most badly documented tool relative to how much documentation is actually produced. It is badly worded, confusing.

In this PR, ChatGPT and I - in close collaboration - implement a parametrizable isoDate schema for Zod and Ajv.

It survives the Zod->Ajv transformation by carrying over the required parameters in the description field of the JSON Schema.

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I suggest moving basic Ajv-related logic to js-lib, since with the current setup js-lib imports into nodejs-lib which is not a good direction - even though this is only in tests.

This is because zod and ajv are very closely coupled for us, i.e. we should not implement a zod feature that will be missing in Ajv - so I have to keep these tests closely together.

By moving getAjv() et al to js-lib, this circular dependency would be solved.
We can leave AjvSchema in nodejs-lib, if we want

[kirillgroshkov]

Let's discuss in a call. The magic levels of this PR are nearing the maximum Hogwards-approved levels ⚠️

[kirillgroshkov]

p3: I prefer else if, which skips evaluating more conditions as soon as it encountered one truthy condition (since they are mutually exclusive)

[kirillgroshkov]

Just a note that I'm afraid of the performance implications.
In reality we deal with hundreds/thousands of isoDates per "validation run", so, it's very performance-sensitive code, I'd like to scrutinize it.

For example, we could get away with just string comparisons and not relying on LocalDate api.

isValidString can be instead done via regex?

Also, I'd like a fast-pass for case when there are no parameters