[frontend] Add info message of starting date mandatory on scenario

[savacano28]

…port

Proposed changes

• Add message info
• Modify file name of mapper exports

Related issues

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.

Project coverage is 28.02%. Comparing base (b597647) to head (6c32646).

Files	Patch %	Lines
...rc/main/java/io/openbas/rest/mapper/MapperApi.java	0.00%	4 Missing ⚠️
...io/openbas/rest/mapper/form/ExportMapperInput.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1319      +/-   ##
============================================
- Coverage     28.02%   28.02%   -0.01%     
  Complexity     1273     1273              
============================================
  Files           513      513              
  Lines         13269    13272       +3     
  Branches        779      780       +1     
============================================
  Hits           3719     3719              
- Misses         9387     9390       +3     
  Partials        163      163              

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