Fix delta external table kind detection (#162)

* Fix delta external table kind detection

The KQL case expression compared tolower(TableType) against "Delta"
(capitalized), which never matches since tolower() produces "delta".
This caused all delta external tables to be incorrectly loaded as
kind=storage.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Update KustoSchemaTools/Parser/KustoLoader/KustoExternalTableBulkLoader.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 3 people

KustoSchemaTools/Parser/KustoLoader/KustoExternalTableBulkLoader.cs

@@ -4,7 +4,7 @@ namespace KustoSchemaTools.Parser.KustoLoader
 {
     public class KustoExternalTableBulkLoader : KustoBulkEntityLoader<ExternalTable>
     {
-        const string LoadExternalTables = ".show external tables | extend Properties = parse_json(Properties), ConnectionString=tostring(parse_json(ConnectionStrings)[0]) | project EntityName = TableName, Folder, DocString, Kind = case(tolower(TableType)  == \"sql\", \"sql\", tolower(TableType)  ==\"Delta\", \"delta\", \"storage\"), DataFormat = tolower(tostring(Properties.Format)), FileExtentions = tostring(Properties.FileExtension), IncludeHeaders = tostring(Properties.IncludeHeaders), Encoding = tostring(Properties.Encoding), NamePrefix = tostring(Properties.NamePrefix), Compressed = tobool(Properties.Compressed), SqlTable = tostring(Properties.TargetEntityName), CreateIfNotExists = tobool(Properties. CreateIfNotExists), PrimaryKey = tostring(Properties.PrimaryKey), SqlDialect = tostring(Properties.SqlDialect), Properties | project EntityName, Body = bag_pack_columns(Folder, DocString, Kind, DataFormat,FileExtentions, IncludeHeaders, Encoding, NamePrefix, Compressed, SqlTable, CreateIfNotExists, PrimaryKey, SqlDialect, Properties)";
+        const string LoadExternalTables = ".show external tables | extend Properties = parse_json(Properties), ConnectionString=tostring(parse_json(ConnectionStrings)[0]) | project EntityName = TableName, Folder, DocString, Kind = case(tolower(TableType)  == \"sql\", \"sql\", tolower(TableType)  ==\"delta\", \"delta\", \"storage\"), DataFormat = tolower(tostring(Properties.Format)), FileExtensions = tostring(Properties.FileExtension), IncludeHeaders = tostring(Properties.IncludeHeaders), Encoding = tostring(Properties.Encoding), NamePrefix = tostring(Properties.NamePrefix), Compressed = tobool(Properties.Compressed), SqlTable = tostring(Properties.TargetEntityName), CreateIfNotExists = tobool(Properties. CreateIfNotExists), PrimaryKey = tostring(Properties.PrimaryKey), SqlDialect = tostring(Properties.SqlDialect), Properties | project EntityName, Body = bag_pack_columns(Folder, DocString, Kind, DataFormat,FileExtensions, IncludeHeaders, Encoding, NamePrefix, Compressed, SqlTable, CreateIfNotExists, PrimaryKey, SqlDialect, Properties)";
         const string LoadExternalTableAdditionalData = ".show database schema as csl script | where DatabaseSchemaScript contains \".create external table\" or DatabaseSchemaScript contains \".create-or-alter external table\" | parse DatabaseSchemaScript with * \"pathformat = \" PathFormat:string \"\\n\"* | parse DatabaseSchemaScript with * \"partition by \" Partitions:string \"\\n\"* | parse DatabaseSchemaScript with *\"h@\\\"\" ConnectionString:string \"\\\"\"* | parse DatabaseSchemaScript with * \".create\" * \"external table \" Table:string \" (\" Columns:string \")\"* | mv-apply S=split(Columns,\",\") to typeof(string) on (extend C = split(S, ':') | extend B=bag_pack(trim('\\\\W',tostring(C[0])), C[1]) | summarize Schema=make_bag(B)) | extend  Partitions = trim(\"[\\\\(\\\\)\\\\r]\",Partitions), PathFormat = trim(\"\\\\)\",trim(\"\\\\r\",trim(\"\\\\(\",PathFormat))) | project EntityName=Table, Body= bag_pack_columns(Schema, ConnectionString, Partitions, PathFormat)";
 
         public KustoExternalTableBulkLoader() : base(d => d.ExternalTables) { }