Issue Summary

When a field has an ampersand '&' the API used to fetch field suggestions fails to return any results as it does not encode the '&' properly. 

Example field name: "Multi choice select&list"

URL constructed for suggestions: https://site.atlassian.net/rest/api/latest/jql/autocompletedata/suggestions?fieldName=Multi%20choice%20select&list[Select%20List%20(multiple%20choices)]&fieldValue=a 

Note the '&' after "select" and before "list" in the above URL is not encoded, thus is interpreted as a parameter separator, instead of the actual character.

Steps to Reproduce

1. Create a custom field with a '&' character
2. Use Advanced JQL search and notice suggestions for custom field options fail

Expected Results

Ampersands should be encoded properly so proper field value suggestions are returned

Actual Results

Ampersands are not properly encoded, return object will always be an empty array

Workaround

Remove ampersands from custom field names