feature/preview screen for import

[shubhrathasetty]

#16

[WaQasRPL]

please resolve conflicts

[rparse]

As per ticket description, I guess after selecting excel file we need to show preview like below -

currently you are showing like below -

Please confirm!

[rparse]

Please confirm the requirement as per my comment, Thank you!

[tdegrunt]

Just one comment, otherwise it seems fine

[rparse]

Tested and found below -

1. If we are uploading blank file then no need to show preview screen/ further processing I guess or any message which states there is no data.

2. If I upload blank file getting preview screen and after I click on upload getting below error - undefined method `reject’ for nil:NilClass
   

3. On staging if I upload uploaded product result sheet(Its accept as it is having same headers) excel it gives me this Exception: undefined method []' for nil..... On this branch if I upload uploaded product result sheet it gives me - preview screen as below and after upload gives this error - Exception: undefined method []' for nil:NilClass value = strip_tags(value.strip) if value.respond_to?(:strip) && columns[column]&.options[:strip_tags] != false ^^^^^^^^^^^^^
   
   Thank you!

[shubhrathasetty]

fixed above errors . thank you

[rparse]

1. Preview structure is fine now, but one column is unselected even if it is having value, so I guess this will be in case of columns having false value (here import_errors column) or we can also disable this columns starting with "import_"
   

2. and after uploading result sheet file it is already uploaded then its give error in excel but with mismatch row and header format