Connect to Jira with Power BI - code for a function

I've made an updated version of the funciton that uses the v3 API (the old one is deprecated). Also runs a bit quicker.

Instructions on how to use this function:

1. Copy the code below into a blank query in Power BI (using the advanced editor).
2. Update the 'jiraDomain' variable using advanced editor (near the top of the code) with the domain you see when you login to your Jira.
3. Generate and save an access token as per Manage API tokens for your Atlassian account | Atlassian Support.
4. Invoke the function:
   1. Put the email address you use to login to Jira in the 'jiraUsername'.
   2. Put the token from step 3. above into the 'jiraAccessToken'.
   3. Put a comma demilted list of the fields you want to return in the 'fields' parameter e.g. 'summary, parent, status':
      1. This list is not case sensitive.
      2. You can enter custom field names here.
      3. If you have more than 1 custom field with the same name it will return both fields with the custom field id added as a suffix.
   4. Add a JQL statement that specifies the issues you want to return.
      1. If you want to return everything you can enter 'key IS NOT EMPTY'.

let
    Source = (jiraUsername as text, jiraAccessToken as text, fields as text, jql as text) =>
let
//test data
    // jiraUsername = jiraUser,
    // jiraAccessToken = jiraToken,
    // fields = "id, parent, summary",
    // jql = "project = kan",

//!!!UPDATE THE BELOW VARIABLE!!!
    jiraDomain = "https://<your-domain>.atlassian.net",

//authenication
    auth = Binary.ToText(Text.ToBinary(jiraUsername & ":" & jiraAccessToken), BinaryEncoding.Base64),


//convert_field_names_to_ids function
convert_field_names_to_ids = (jiraUsername as text, jiraAccessToken as text, fields as text) =>
let 
    fieldsConverted = if fields = "id" then "key" else Text.Replace(Text.Replace(fields," ,",","),", ",","),

    fieldsToGetAsList = Text.Split(Text.Lower(fieldsConverted),","),
    jiraFieldNameList = Json.Document(Web.Contents(jiraDomain & "/rest/api/3/field", [Headers = [Authorization="Basic " & auth]])),
    fieldRecordsToTable = Table.FromList(jiraFieldNameList, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    expandFieldRecords = Table.ExpandRecordColumn(fieldRecordsToTable, "Column1", {"id", "key", "name"}, {"id", "key", "name"}),
    addGetFieldCheck = Table.AddColumn(expandFieldRecords, "getField?", each List.Contains(fieldsToGetAsList,Text.Lower([name]))),
    filterToFieldsToGet = Table.SelectRows(addGetFieldCheck, each ([#"getField?"] = true)),
    createFieldsString = Text.Combine(Table.Column(filterToFieldsToGet,"id"),",")

in
    createFieldsString,

//get_jira_fields_with_rename_lists

get_jira_fields_with_rename_lists = (jiraUsername as text, jiraAccessToken as text)=>
let
    auth = Binary.ToText(Text.ToBinary(jiraUsername & ":" & jiraAccessToken), BinaryEncoding.Base64),

    jiraFieldNameList = Json.Document(Web.Contents(jiraDomain & "/rest/api/3/field", [Headers = [Authorization="Basic " & auth]])),
    fieldRecordsToTable = Table.FromList(jiraFieldNameList, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    expandFieldRecords = Table.ExpandRecordColumn(fieldRecordsToTable, "Column1", {"id", "key", "name"}, {"id", "key", "name"}),
    #"Added Custom" = Table.AddColumn(expandFieldRecords, "renameList", each if List.Count(let name = [name] in Table.Column(Table.SelectRows(expandFieldRecords, each ([name] = name)),"name"))>1 then {[id],[name] & " (" & [id] & ")"} else {[id],[name]})
in
    #"Added Custom",

//field variables
    fields_list = Text.Lower(Text.Replace(Text.Replace(fields," ,",","),", ",",")),
    id_or_key_request = fields_list = "id" or fields_list = "key" or fields_list = "id,key" or fields_list = "key,id",
    fields_for_query = if fields = null or id_or_key_request then {"key"} else List.RemoveItems(Text.Split(convert_field_names_to_ids(jiraUsername, jiraAccessToken, fields_list), ","), {"issuekey"}),

    get_issues_list_function = (optional next_page_token as text) =>
        Json.Document(Web.Contents(jiraDomain & "/rest/api/3/search/jql",
            [
                Headers = [
                    Authorization="Basic " & auth,
                    #"Content-Type" = "application/json"
                ],
                Content = Json.FromValue(
                    [
                        jql = jql,
                        maxResults = 5000,
                        fields = fields_for_query,
                        nextPageToken = next_page_token
                    ]
                )
            ]
        )),


    get_issues = 
        List.Generate(
            () => get_issues_list_function(),
            each Record.HasFields(_, "issues"),
            each try get_issues_list_function(_[nextPageToken]) otherwise []
        ),
    #"Converted to Table" = Table.FromList(get_issues, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    #"Expanded Column1" = Table.ExpandRecordColumn(#"Converted to Table", "Column1", {"issues"}, {"issues"}),
  #"Expanded issues" = Table.ExpandListColumn(#"Expanded Column1", "issues"),
  #"Expanded issues 1" = Table.ExpandRecordColumn(#"Expanded issues", "issues", {"id", "key", "fields"}, {"id", "key", "fields"}),
  #"Expanded fields" = if id_or_key_request then #"Expanded issues 1" else Table.ExpandRecordColumn(#"Expanded issues 1", "fields", fields_for_query),
  rename_list = Table.SelectRows(get_jira_fields_with_rename_lists(jiraUser, jiraToken), each List.Contains(fields_for_query, [key]))[renameList],
  #"Renamed columns" = Table.RenameColumns(#"Expanded fields", rename_list)
in
    #"Renamed columns"
in
    Source