CIP-0057 | Fix schema validation error (strict mode)

[Unisay]

This PR fixes a subtle mistake in the JSON schema that is caught by the popular JSON schema validator ajv:

Error: strict mode: missing type "object" for keyword "required" at "https://cips.cardano.org/cips/cip57/schemas/plutus-builtin.json#" (strictTypes)
    at checkStrictMode (/home/yura/projects/cardano/plutus/node_modules/ajv/dist/compile/util.js:174:15)
    at strictTypesError (/home/yura/projects/cardano/plutus/node_modules/ajv/dist/compile/validate/index.js:286:32)
    at checkKeywordTypes (/home/yura/projects/cardano/plutus/node_modules/ajv/dist/compile/validate/index.js:262:17)
    at checkStrictTypes (/home/yura/projects/cardano/plutus/node_modules/ajv/dist/compile/validate/index.js:234:5)
    at schemaKeywords (/home/yura/projects/cardano/plutus/node_modules/ajv/dist/compile/validate/index.js:189:9)
    at typeAndKeywords (/home/yura/projects/cardano/plutus/node_modules/ajv/dist/compile/validate/index.js:128:5)
    at /home/yura/projects/cardano/plutus/node_modules/ajv/dist/compile/validate/index.js:70:9
    at CodeGen.code (/home/yura/projects/cardano/plutus/node_modules/ajv/dist/compile/codegen/index.js:439:13)
    at /home/yura/projects/cardano/plutus/node_modules/ajv/dist/compile/validate/index.js:37:166
    at CodeGen.code (/home/yura/projects/cardano/plutus/node_modules/ajv/dist/compile/codegen/index.js:439:13)

See the context and example here: ajv-validator/ajv#1553 (comment)

I've added explicit "type": "object" in a few places and it fixes the validation error.

[rphair]

@Unisay this commit history includes c65b5dd from your earlier #768. That commit should be removed or reverted in this branch so these two PR's can be considered separately.

[Unisay]

That commit should be removed or reverted in this branch so these two PR's can be considered separately.

@rphair done!

[Ryun1]

Any chance this could break backwards compatibility?

[Unisay]

Any chance this could break backwards compatibility?

The only possibility I can imagine is that somebody relied on the fact that without explicit "type": "object" any value that is not an object was valid against the schema, which is highly unlikely.

[rphair]

This seems logical & isn't believed by our CIP meeting attendees now to be likely to break anything.

[Ryun1]

This seems unlikely to cause an issue with backwards compatibility, lets merge :)