✨ [RUM-5775] Make view local context writable

[cy-moi]

Motivation

Enable users to set the view specific context with existing apis:

• startView({...options, context})
• beforeSend: (e) => {}

Changes

• Add customer context in view collection
• Add USER_CUSTOMIZABLE_FIELD_PATHS for view in event assembly
• Add feature flag view_specific_context

Testing

• Local
• Staging
• Unit
• End to end

---

I have gone over the contributing documentation.

[cit-pr-commenter]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	160.16 KiB	160.44 KiB	296 B	+0.18%	✅
Logs	55.98 KiB	56.02 KiB	48 B	+0.08%	✅
Rum Slim	108.76 KiB	109.05 KiB	296 B	+0.27%	✅
Worker	25.21 KiB	25.21 KiB	0 B	0.00%	✅

🚀 CPU Performance

Action Name	Base Average Cpu Time (ms)	Local Average Cpu Time (ms)	𝚫
addglobalcontext	0.002	0.002	-0.000
addaction	0.042	0.036	-0.005
addtiming	0.001	0.001	0.000
adderror	0.047	0.048	0.001
startstopsessionreplayrecording	1.316	1.133	-0.184
startview	1.422	1.198	-0.224
logmessage	0.025	0.023	-0.002

🧠 Memory Performance

Action Name	Base Consumption Memory (bytes)	Local Consumption Memory (bytes)	𝚫 (bytes)
addglobalcontext	20.23 KiB	21.23 KiB	1022 B
addaction	69.70 KiB	70.70 KiB	1.00 KiB
addtiming	15.81 KiB	20.11 KiB	4.30 KiB
adderror	82.47 KiB	86.39 KiB	3.92 KiB
startstopsessionreplayrecording	12.77 KiB	11.79 KiB	-1009 B
startview	347.02 KiB	350.86 KiB	3.84 KiB
logmessage	68.87 KiB	70.99 KiB	2.12 KiB

🔗 RealWorld

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.48%. Comparing base (6b3cfef) to head (70826ae).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2939      +/-   ##
==========================================
- Coverage   93.48%   93.48%   -0.01%     
==========================================
  Files         271      271              
  Lines        7616     7623       +7     
  Branches     1696     1700       +4     
==========================================
+ Hits         7120     7126       +6     
- Misses        496      497       +1     

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[BenoitZugmeyer]

💬 suggestion: ‏‏I'm not a big fan of the customer prefix here. Other properties of this interface also come from the customer, so it feels weird to specify customer for context.

I understand you are using customerContext instead of context to avoid having a context field on an interface that is already called xxxContext? I agree that's too many context! But I would rather rename ViewContext to something like ViewHistoryEntry (as I suggested in the RFC) instead of using customerContext.

[cy-moi]

I'm moving this renaming to another PR. Still in draft: #2953