Add object validation keywords

[crmne]

Goal

Add support for object-specific Draft 2020-12 validation keywords:

• minProperties
• maxProperties
• patternProperties
• propertyNames

Meanings

minProperties and maxProperties constrain how many keys an object may have.

patternProperties says: for keys matching this pattern, their values must match this schema.

propertyNames says: every key name itself must validate against a schema.

These last two are related, but not the same:

• patternProperties validates values selected by matching key names.
• propertyNames validates the key names themselves.

Proposed DSL for property counts

object :metadata, min_properties: 1, max_properties: 5 do
  string :name
end

Proposed DSL for patternProperties

object :metadata do
  keys_matching /^x-/ do
    string
  end

  keys_matching /^count_/ do
    integer minimum: 0
  end
end

This means:

• keys like x-name must have string values
• keys like count_views must have integer values

Open DSL question for propertyNames

We need a clear DSL for validating all key names. key_pattern: may not be clear enough, especially next to keys_matching.

Possible options:

object :metadata do
  keys do
    string pattern: "^[a-z_]+$"
  end
end

or:

object :metadata, keys: { pattern: "^[a-z_]+$" } do
  string :name
end

Acceptance criteria

• Exact generation tests for all supported object keywords.
• Behavior tests for valid and invalid objects.
• Generated schemas validate against Draft 2020-12.
• Final propertyNames DSL is decided before implementation.