Add NOT NULL constraint on project.organization_id column

What does this MR do and why?

Adds a NOT NULL constraint on the projects.organization_id column. This guarantees that projects would always belong to an organization moving forward (Organizations For Cells Blueprint)

References

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• Closes #502514 (closed)
• Closes #499665 (closed)

MR acceptance checklist

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Screenshots or screen recordings

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How to set up and validate locally

1. Run the migrations by running bin/rails db:migrate RAILS_ENV=development
2. A not null constraint should be added to the projects table. This can be verified using the following query:

SELECT 
    c.conname AS constraint_name,
    t.relname AS table_name,
    pg_get_constraintdef(c.oid) AS constraint_definition
FROM 
    pg_constraint c
JOIN 
    pg_class t ON c.conrelid = t.oid
JOIN 
    pg_namespace n ON t.relnamespace = n.oid
WHERE 
    c.conname = 'check_1a6f946a8a';