feat: use transactions when writing to the database

[zacharygolba]

This PR introduces a public transaction api to the model class. Changes are backwards
compatible with the previous model api.

Internally, all methods that modify the state of the database are wrapped in transactions.
If the transaction fails, all calls to create, save, or update will be rolled back to
the state before the transaction began.

Example:

import User from 'app/models/user';

// This internally uses a transaction.
await User.create({
  firstName: 'New',
  lastName: 'User'
});

Working With Transactions

You have the ability to manually specify the transaction that will be used for a
create, update, or save call with the static and instance method, transacting.

Example:

import { Model } from 'lux-framework';

import Profile from 'app/models/profile';

class User extends Model {
  static hasOne = {
    profile: {
      inverse: 'user'
    }
  };

  static hooks = {
    async beforeCreate(user, trx) {
      // If the transaction fails the profile instance will not be persisted.
      user.profile = await Profile
        .transacting(trx)
        .create();
    }
  };
}

You can also manually trigger create a transaction if you plan on creating many
model instances as once.

Example:

import User from 'app/models/user';

User.transaction(trx => (
  Promise.all([
    User
      .transacting(trx)
      .create({
        firstName: 'New',
        lastName: 'User'
      }),
    User
      .transacting(trx)
      .create({
        firstName: 'New',
        lastName: 'User'
      }),
    User
      .transacting(trx)
      .create({
        firstName: 'New',
        lastName: 'User'
      })
  ])
));

[seawatts]

Is this just for debugging?

[zacharygolba]

correct

[codecov-io]

Current coverage is 90.03% (diff: 95.91%)

Merging #527 into master will increase coverage by 1.11%

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+ Hits           1644       1734    +90   
+ Misses          205        192    -13   
  Partials          0          0          

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[kev5873]

Just wondering if this could be embedded into L132?

[zacharygolba]

This takes care of edge cases where hooks is null, 0, false or any other falsy value besides undefined. Those edge cases should never occur but this accounts for them just in case.

Destructed defaults only work if the value is undefined.

[kev5873]

There's another log here, just fyi.

[zacharygolba]

Nice find!

[kev5873]

Everything else looks good to me