The backend allows for any kind of string in the dosage field in the prescription.

[AshrafMd-1]

Describe the bug
The backend currently accepts any kind of string for dosage in the prescription making the dosage values malfunction.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
The backend must sanitise the dosage values before saving them in the DB

Screenshots
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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
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