feat: add existing components to unit [FC-0083]

[rpenido]

Description

This PR allows adding existing components to units

Additional Information

• Implements Add existing component to unit #1620
• Depends on feat: Add component to Unit [FC-0083] #1784

Testing instructions

• Go to the library home of a library.
• Create a Unit.
• Open the Unit page of the new unit.
• Click on Add content button.
• Click on "Existing Library Content"
• Select some components and click on "Add to Unit"
• Verify that the blocks are added to the unit

Note: Before merging #1797 you may see another Units on the component picker

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Private ref: FAL-4059

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.58%. Comparing base (aa8a5bf) to head (dfa4dca).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1811   +/-   ##
=======================================
  Coverage   93.57%   93.58%           
=======================================
  Files        1139     1139           
  Lines       23310    23324   +14     
  Branches     5038     5027   -11     
=======================================
+ Hits        21813    21828   +15     
- Misses       1421     1428    +7     
+ Partials       76       68    -8     

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[DanielVZ96]

besides the same unit appearing in the selection modal, i saw no other issues. lgtm! let me know when that other PR is merged

[pomegranited]

@rpenido would you be able to address Sam's comment on @ChrisChV 's issue here?
#1619 (comment)

[rpenido]

@rpenido would you be able to address Sam's comment on @ChrisChV 's issue here? #1619 (comment)

Sure @pomegranited! Fixed here: 504cd32

I also fixed a bug that the "Open" button on the Unit Sidebar didn't work inside a collection.