Combine submission middlewares into controllers

[liangyuanruo]

Blocked by #144

Many of our middleware functions are being chained together and used as services, which is an anti-pattern. This causes problems such as having long-range object and type dependencies, which must be overridden by the developer with type assertions.

A better solution where possible, is to merge middlewares into a single controller function as far as possible so that dependencies are clearly defined.

[arshadali172]

• Webhook controller should be removed and webhook service referenced in the submission controller

[liangyuanruo]

@karrui @tshuli i had a discussion with @mantariksh today, and we thought that instead of chaining middlewares, we can group relevant parts of the celebrate middleware together.

For example, instead of doing this:

app.route(...).post(
  celebrate({
    body: Joi.object({
        valueA: Joi.string(),
        valueB: Joi.boolean()
    })
  })
  middlewareUsingValueA, // naked middleware function with implicit
  middlewareUsingValueB, // dependency on upstream middleware for protection
)

We can do this instead:

// Exported together so that it's not possible to
// use middleware without protection
export const middlewareUsingValueA = [
  celebrate({
    body: Joi.object({
        valueA: Joi.string(),
    })
  }),
  (req, res, next) => {...} // or implemented as a separate function
]

export const middlewareUsingValueB = [
  celebrate({
    body: Joi.object({
        valueB: Joi.string(),
    })
  }),
  (req, res, next) => {...}
]

app.route(...).post(
  middlewareUsingValueA,
  middlewareUsingValueB
)

[liangyuanruo]

@frankchn could we get your help with merging the middlewares for the encrypt mode submission API /v2/submissions/encrypt/:formId([a-fA-F0-9]{24}), following the pattern for the email mode submission API? It's a fairly large refactor, but the end goal should look similar to EmailSubmissionRouter and the handleEmailSubmission function.

Happy to discuss further if necessary!

[liangyuanruo]

Note: to also refactor associated routes for

• VerifiedContentMiddleware.encryptVerifiedSpcpFields
• EncryptSubmissionMiddleware.prepareEncryptSubmission
• encryptSubmissions.saveResponseToDb
• webhookVerifiedContentFactory.post
• SubmissionsMiddleware.sendEmailConfirmations