FEAT: Add legacy .xls support to converter task

[Shivang Nagta (ShivangNagta)]

Description

Adds support for converting legacy Excel 97-2003 (.xls) files to CSV
via a new format: xls on the converter task. The existing xlsx converter uses
excelize, which only reads modern Office Open XML (.xlsx/.xlsm) and cannot
parse the legacy binary .xls format - so a separate handler is required.

Implementation

• New format: xls handler (xls.go),
  backed by github.com/yamitzky/xlrd-go](https://github.com/yamitzky/xlrd-go) - a
  pure-Go port of Python's xlrd.
• Mirrors the xlsx converter's options (sheets, skip_rows, skip_rows_by_sheet,
  sanitize_headers, sanitize_sheet_names) and per-sheet CSV output (one record per
  sheet, sheet name in the xlsx_sheet_name context key).
• Includes hidden sheets
• Since excelise(used in xlsx) returns formatted data (number, dates, booleans) unlike xlrd-go,
  which is a much lower level library providing cell value and cell type instead, we need to perform
  the formatting ourself, so the number of lines of codes is more than expected.

Testing

Created and ran unit tests - TestFormatDate, TestFormatNumber, TestBoolText, TestIsBuiltinDateFormat, TestTrimTrailingEmpty the test file is not included in the commit.

Tested against automotive_browse_tree_guide.xls containing 4 sheets(1 hidden).

YAML used:

tasks:
  - name: read_xls
    type: file
    path: /some_path/automotive_browse_tree_guide.xls
  - name: to_csv
    type: converter
    format: xls
  - name: write_csv
    type: file
    path: /some_path/___CATERPILLAR___CONTEXT___xlsx_sheet_name___.csv

One of the sheet in excel

Its output in csv

All output csv files:

Checks for all supported options:

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation and I have updated the documentation accordingly.
• I have added tests to cover my changes.

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[Mayuresh Pawar (Mayureshpawar29)]

Shivang Nagta (@ShivangNagta) Maintaining a separate fork of grate repo would add quite a bit of overhead. Let's see if we can find an alternative library that supports hyperlink parsing.

[Shivang Nagta (ShivangNagta)]

Shivang Nagta (Shivang Nagta (@ShivangNagta)) Maintaining a separate fork of grate repo would add quite a bit of overhead. Let's see if we can find an alternative library that supports hyperlink parsing.

I get the concern, let me see if i could find something else

[Mahesh Kamble (ma-gk)]

Can you please look into one of the packages from https://pkg.go.dev/

Ref: https://pkg.go.dev/github.com/extrame/xls