feat: support for predefined variables (WIP)

[kishannareshpal]

Important

This is a WIP. I try working on this every weekend, hence the slow progress. The branch will always be up-to-date. If you don't want to wait and are willing to contribute to this PR feel free to checkout the branch and commit (feat/predefined-variable).

References

Closes #3317

Description

Note: Tidy this PR description when work in this PR is finished

The idea is to introduce a feature similar to:

• https://learning.postman.com/docs/writing-scripts/script-references/variables-list/

This feature is being built based on the work done for https://docs.hoppscotch.io/documentation/getting-started/rest/environment-variables.

Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

Additional Information

Remarks

• Predefined variables takes precedence over manually defined environment / secret variables. E.g. If you define an environment / secret variable called $guid while $guid is a predefined variable that computes to a random GUID, the request parser will use the predefined variable over your manually defined variable.

Demonstration

This video demonstrates the use of a Predefined variable in Hoppscotch. At the first instance you will see a usage of a normal environment variable myvar, and after that the video shows the use of a predefined variable called $nowIso which computes to the current time at the time of request. After that, the video also shows the usage of another predefined variable called $guid that computes to a random GUID value (noting that for demonstrations purposed the GUID value is just a simple string random string).

The video also shows a green border with green background on hover highlighting a valid predefined variable, while a red border with a red hover background is shown highlighting an invalid predefined variable. Hovering over a predefined variable name, a brief description is shown.

ScreenRecording2024-03-10at21.46.26-ezgif.com-video-to-gif-converter.mov

[sentry-io]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: packages/hoppscotch-common/src/composables/codemirror.ts

Function	Unhandled Issue
useCodemirror	TypeError: Failed to execute 'decode' on 'TextDecoder': The provided value is not of type '(ArrayBuffer or A... .r... Event Count: 1 Affected Users: 2
useCodemirror	TypeError: Cannot read properties of undefined (reading 'type') responseString(hoppscotch-common/src/components/gr... Event Count: 1 Affected Users: 1

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