add query modifier function support.

[mrfrase3]

Query Modifiers

Sometimes it's important to use an unusual Mongoose Query method, like specifying whether to read from a primary or secondary node, but maybe only for certain requests.

You can access the internal Mongoose Query object used for a find/get request by specifying the queryModifier function. It is also possible to override that global function by specifying the function in a requests params.

// Specify a global query modifier when creating the service
app.use('/messages', service({
  Model,
  queryModifier: (query, params) => {
    query.read('secondaryPreferred');
  },
  queryModifierKey: '__queryModifier__' // default is 'queryModifier'
}));

app.service('messages').find({
  query: { ... },
}).then((result) => {
  console.log('Result from secondary:', result)
});

// Override the modifier on a per-request basis
app.service('messages').find({
  query: { ... },
  __queryModifier__: (query, params) => {
    query.read('primaryPreferred');
  }
}).then((result) => {
  console.log('Result from primary:', result)
});

// Disable the global modifier on a per-request basis
app.service('messages').find({
  query: { ... },
  __queryModifier__: false
}).then((result) => {
  console.log('Result from default option:', result)
});

resolves #407

[daffl]

Sorry almost missed this. It looks good to mee. Can you resolve the conflict and I can get a new minor version out.

[mrfrase3]

Hey @daffl,

I've fixed the merge conflict, I also updated the type definition.

[daffl]

Thank you! Just to clarify, __queryModifier__ is just an example for changing the key and it's params.queryModifier by default right?

[mrfrase3]

Yes, correct. queryModifier is the default

[daffl]

Released as v8.5.0, thank you!