Error message helper

[deepsidhu85]

What does this PR do and why?

Describe in detail what your merge request does and why.

This PR adds in an error_message helper method to the application_controller that can be used across the back-end and front-end for retrieving an object's error message from the attached errors array.

Screenshots or screen recordings

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Ensure the tests pass
2. Try out the different actions which were updated to use this new error_message method and verify the thrown error messages are displayed as expected

PR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the PR acceptance checklist for this PR.

[github-actions]

Code Metrics Report

Coverage	Test Execution Time
92.8%	10m7s

Code coverage of files in pull request scope (94.6%)

Files	Coverage
app/controllers/application_controller.rb	95.1%
app/controllers/concerns/attachment_actions.rb	98.4%
app/controllers/concerns/bot_actions.rb	97.6%
app/controllers/concerns/bot_personal_access_token_actions.rb	97.6%
app/controllers/concerns/membership_actions.rb	96.4%
app/controllers/concerns/share_actions.rb	94.0%
app/controllers/data_exports_controller.rb	96.8%
app/controllers/groups_controller.rb	90.4%
app/controllers/profiles/personal_access_tokens_controller.rb	100.0%
app/controllers/projects/samples/attachments/concatenations_controller.rb	100.0%
app/controllers/projects/samples/attachments_controller.rb	93.0%
app/controllers/projects/samples/deletions_controller.rb	94.5%
app/controllers/projects/samples/metadata/deletions_controller.rb	93.3%
app/controllers/projects/samples/metadata/fields_controller.rb	92.5%
app/controllers/projects_controller.rb	91.9%
app/views/projects/samples/attachments/deletions/destroy.turbo_stream.erb	100.0%
app/views/projects/samples/metadata/destroy.turbo_stream.erb	77.7%
app/views/projects/samples/metadata/fields/update.turbo_stream.erb	100.0%

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Reported by octocov