Enable strictNullChecks in API tsconfig.json

[marrouchi]

Currently, the strictNullChecks flag in the tsconfig.json file for the API is not enabled. This means that null and undefined are treated as assignable to other types, which can potentially lead to bugs that are only caught at runtime.

By enabling strictNullChecks: true, we can enforce more robust type safety in the codebase by explicitly handling null and undefined cases. This will improve code quality, reduce runtime errors, and align with TypeScript best practices.

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Acceptance Criteria:

1. Update the tsconfig.json file to enable the strictNullChecks flag:

   {
       "compilerOptions": {
           "strictNullChecks": true
       }
   }

2. Ensure all TypeScript files in the API codebase comply with this new setting by updating types and adding null/undefined handling where required.
3. Verify that the application compiles successfully with no TypeScript errors.
4. Run all tests to confirm no functionality is broken after enabling this setting.

Modules

WebSocket

• ✅

Analytics

• ✅

bot-stats

• ✅

Settings

• ✅

i18n

• ✅

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CMS

• ContentType ✅
• Content ✅
• Menu

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Chat

• Category ✅
• Label ✅
• ContextVar
• Block
• Message
• Conversation
• Bot
• Subscriber

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Attachment

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Channels

• base-web-channel ✅
• slack
• messenger
• whatsapp

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Plugins

• pluginService/helper ✅
• nlp/nlu
• external repos

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Utils

• Generics
• utils

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User Module

• auth
• permission
• role
• invitation
• model
• password

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Generic

• base-controller
• base-seeder

Errors

• "does not exist on type 'unknown'" (14 occurrences)