refactor: reduce memory usage

[wa0x6e]

🧿 Current issues / What's wrong ?

In helpers/spaces.ts, we're storing a duplicate array for ranked spaces, increasing memory usage.

💊 Fixes / Solution

We already have a full spaces object, ranked spaces are just a subset of that object, in a specific order. Instead of saving the ranked spaces as an array of object, we could just save the ranked space Ids in an array, reducing the memory usage.

🚧 Changes

• Convert rankedSpaces from an an array of spaces to an array of space IDs.
• Reduce the number of property in spacesMetadata to only the one currently used

Todo

• Need to add more tests
• Ultimate goal will be to remove the spaces cache entirely

🛠️ Tests

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 37 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/graphql/operations/ranking.ts	0.00%	20 Missing ⚠️
src/helpers/spaces.ts	0.00%	14 Missing ⚠️
src/graphql/helpers.ts	0.00%	3 Missing ⚠️

Additional details and impacted files

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