How to Get Jira Issue Field Value in PowerQuery M

JiraFieldName2Id.pq

(FieldName as text) as text =>
let
    Source = Json.Document(Web.Contents(JiraRootUrl & "/rest/api/latest/field")),
    #"Converted to Table" = Table.FromList(Source, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
    #"ExpandedTable" = Table.ExpandRecordColumn(#"Converted to Table", "Column1", {"id", "name"}, {"id", "name"}),
    Record = Table.First(Table.SelectRows(ExpandedTable, each ([name] = FieldName))),
    FieldId = Record.Field(Record,"id")
in
    FieldId

JiraGetFieldValueByName.pq

(IssueKey as text, FieldName as text) =>
let
    FieldId = JiraFieldName2Id(FieldName),
    Source = Json.Document(Web.Contents(JiraRootUrl & "/rest/api/2/issue/" & IssueKey & "?fields=" & FieldId)),
    fields = Source[fields],
    Field = Record.Field(fields,FieldId),
    FieldValue = if Field = null then null else Record.Field(Field,"value")
in
    FieldValue

See explanation in blog post https://tdalon.blogspot.com/2022/06/jira-powerquery-get-field-value.html