Fix mutation in timeline reducer

[Abishekcs]

What this PR does

Fixes mutation in timeline reducer(s) which are handling the action RESET_TITLES & UPDATE_TITLE.

Cause Bug

For this finding the cause of bug was easy as the error message exaclty indicated where mutation was as shown below:

For RESET_TITLES:

For UPDATE_TITLE:

The spread operator doesn’t work as expected with deeply nested objects because it copies the values of the top-level properties of weeks to new addresses/references, but the inner objects retain the same addresses/references.

Fix

Resolved by using lodash cloneDeep.

• Why the changes in TimelineHandler component?
  • In Redux:
    • Mutation: Changes are immediate since we were previously directly modifying the same object reference -
      any code holding that reference sees the changes instantly.
    • Immutable: Creates a new object reference, requiring React/Redux to process and batch the state update,
      making the changes not immediately available. Also, after resetting the timeline week titles, the saveTimeline
      was called immediately, leading to an API call right away. During this time, Redux had not yet received the
      new updates.

Note:

While testing this #6138 changes should be available😅 or else /timeline page may not work.(KEEPPING IT IN DRAFT UNTIL THEN & ALSO MANY TEST ARE FAILING FOR THIS)

Screenshots

Before:

Before.mp4

After:

After.mp4