Fix pre-selected item when using belongs_to

[pierrickouw]

Thanks for the great lib!
We use it a lot in our application and found a small issue when using belongs_to in active admin.

-> To make belongs_to works with the lib, we have to add path_params in the ajax options (as described here). But this example doesn't work when the Model already have a value (it is not preselected). It works well for subsequent search.

-> This is because https://github.com/codevise/activeadmin-searchable_select/blob/master/lib/activeadmin/searchable_select/select_input_extension.rb#L87 is taking into account only the params and not the path_params during initial load.

---

In our code, to fix it we had to add it twice, which we guess is not intended:

            f.input(:option_value,
                    as: :searchable_select,
                    ajax: {
                      resource: OptionValue,
                      path_params: {
                        option_type_id: f.object.product.option_type_id
                      },
					 params: {
					  option_type_id: f.object.product.option_type_id
					}
                    })

cc @ChrLec

[tf]

Sorry for the delay. Makes sense. Will publish a new version later today.

[tf]

For some reason, GitHub did not trigger the test workflow for this PR. I therefore did not notice that the specs contained a syntax error (extra opening do here). Fixing that, I kept running into the error described in this commit. Did you see this locally? Moved the new spec to the end-to-end test to work around the problem in #44.

Released as 1.7.0.

[pierrickouw]

Sorry for the typo, I guess it went in just before pushing, thanks for the merge!