Add validation for output file path / name

[szh]

Note: This depends on #381

Implemented Changes

Implement validation on the annotation specifying output file path / name and make sure there are tests for the following cases:

• File name must be unique across secret groups (including secret groups that are using default file paths)
• The path is a valid Linux filename (check length)

Also ensure that if you are using a non-custom (i.e. non-templatized) file format (or using the default yaml template), and:

• If you don't specify the output file path annotation, then you get a default filepath of the form <secret-group-name>.<file-type>.
• If you do specify the output file path annotation, this (explicit) output file path annotation takes precedence over the default output file path for that file format (i.e. BOTH the file directory and file name are overridden).

Connected Issue/Story

CyberArk internal issue link: ONYX-13143

Changelog

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Test coverage

• This PR includes new unit and integration tests to go with the code
  changes, or
• The changes in this PR do not require tests

Documentation

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Behavior

• This PR changes product behavior and has been reviewed by a PO, or
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Security

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[codeclimate]

Method SecretGroup.absoluteFilePath has 5 return statements (exceeds 4 allowed).

[doodlesbykumbi]

PR looking good. Left some comments

[codeclimate]

Code Climate has analyzed commit 02e7fcb and detected 1 issue on this pull request.

Here's the issue category breakdown:

Category	Count
Complexity	1

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 90.4% (0.3% change).

View more on Code Climate.