fix: request schema preprocessor and multipart middleware custom formats

[LEI]

Not sure about this, but the formats seems required for the request schema preprocessor and the multipart middleware ajv instances.

Moreover, I could not catch the RequestSchemaPreprocessor error (unhandled rejection):

Error: unknown format "bigint" is used in schema at path "#/properties/id"
    at Object.generate_format [as code] (./node_modules/ajv/lib/dotjs/format.js:69:15)
    at Object.generate_validate [as validate] (./node_modules/ajv/lib/dotjs/validate.js:374:35)
    at Object.generate_properties [as code] (./node_modules/ajv/lib/dotjs/properties.js:201:26)
    at generate_validate (./node_modules/ajv/lib/dotjs/validate.js:374:35)
    at localCompile (./node_modules/ajv/lib/compile/index.js:88:22)
    at Ajv.compile (./node_modules/ajv/lib/compile/index.js:55:13)
    at Ajv._compile (./node_modules/ajv/lib/ajv.js:348:27)
    at Ajv.getSchema (./node_modules/ajv/lib/ajv.js:204:54)
    at RequestSchemaPreprocessor.traverse (./node_modules/express-openapi-validator/dist/middlewares/parsers/request.schema.preprocessor.js:88:30)
    at RequestSchemaPreprocessor.cleanseContentSchema (./node_modules/express-openapi-validator/dist/middlewares/parsers/request.schema.preprocessor.js:82:14)

Finally, I updated the MultipartOpts type in the second commit to accept the ajv options as a property (ajvOpts).

[cdimascio]

@LEI thanks. this is definitely the right idea. i ended building upon you change to extract the ajv options into common handler class, so that future modifications can be made more easily across the various internal middlewares.

[cdimascio]

@all-contributors add @LEI for code

[allcontributors]

@cdimascio

I've put up a pull request to add @LEI! 🎉