Unable to create dynamic function parameters in Power BI Custom Connector

I am trying to get the dropdown to be populated by another function and am getting a Microsoft.Mashup.Engine.Interface.UnpermittedResourceAccessException (I believe means forbidden access) or a grayed out dropdown.

It seems like there was already someone trying to do this (https://github.com/microsoft/DataConnectors/issues/70 and Use-an-API-Call-to-Populate-Custom-Data-Connector-Settings/), but no one appears to have solved this issue. The main problem I believe is that you are trying to call a function from within a type definition. It doesn't seem to work for me, so does anyone have any ideas?

Here is my complete test source code. The API is public so anyone can try running this.

// This file contains your Data Connector logic
section IssueTest;

DefaultRequestHeaders = [
    #"Accept" = "application/json"
];

[DataSource.Kind="IssueTest", Publish="IssueTest.Publish"]
shared nothing = () =>
    let 
        a = "Hello From Issue Post"
    in
        a;

[DataSource.Kind="IssueTest"]
shared IssueTest.Contents = Value.ReplaceType(IssueImpl, IssueType);

IssueType = type function (
    optional employee as (type text meta [
        Documentation.FieldCaption = "Pick Employee",
        Documentation.AllowedValues = getEmployees // also tried * = employees which gives (Microsoft.Mashup.Engine.Interface.UnpermittedResourceAccessException)
    ]))
    as text meta [
        Documentation.Name = "IssueTest"
    ];


IssueImpl = (optional employee as text) =>
    let
        a = getEmployees()
    in
        a;


[DataSource.Kind="IssueTest"]
getEmployees = () =>
    let
        Source = Web.Contents("https://gorest.co.in/public-api/users/"),
        Parsed = Json.Document(Source),
        Result = Parsed[result],
        Table = Table.FromValue(Result),
        Column = Table.RemoveColumns(Table,{"Value"}),
        List = Table.ToList(Column),
        Buffer = List.Buffer(List)
        // Check = Buffer{0} is text // Check if the list is filled with text values
    in
        Buffer;

// This gives a mashup exception (Microsoft.Mashup.Engine.Interface.UnpermittedResourceAccessException)
// [DataSource.Kind="IssueTest"]
// shared empl = employees;

employees = 
    let
        Source = Web.Contents("https://gorest.co.in/public-api/users/"),
        Parsed = Json.Document(Source),
        Result = Parsed[result],
        Table = Table.FromValue(Result),
        Column = Table.RemoveColumns(Table,{"Value"}),
        List = Table.ToList(Column),
        Buffer = List.Buffer(List)
        // Check = Buffer{0} is text // Check if the list is filled with text values
    in
        Buffer;


// Data Source Kind description
IssueTest = [
    Authentication = [
        // UsernamePassword = [], // will end up needing to use Basic Auth
        Implicit = []
    ],
    Label = Extension.LoadString("DataSourceLabel")
];

// Data Source UI publishing description
IssueTest.Publish = [
    ...
];

IssueTest.Icons = [
    ...
];