♻️ add the register endpoint validation

Description

I have added the register endpoint validation like email checks, password character checks in proper json format so that it's easy to show them in the frontend.

Fixes #14 (closed)

Type of change

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• 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 not work as expected)
• This change requires a documentation update

Checklist

• I have read the CONTRIBUTING document
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Licensing of Contributed Material

By submitting this pull request, I confirm that my contribution is licensed under the same terms as the rest of the project, as described in the repository's top-level LICENSE file.

Branching

• I have created a new branch for my work
• My branch is based on the appropriate branch (e.g., bug fixes based on the oldest supported release line, new features based on 'main')

Documentation

• I have updated the documentation accordingly
• I have included versionadded/versionchanged ReST directives at the bottom of any new or changed Python docstrings

Steps to test feature

How can we test the feature implemented in this PR? Mention steps to test it.

Additional Context

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