Replace constructor functions with methods

[TomNicholas]

It's generally a bit confusing that there are multiple ways to make most classes, e.g. local_filesystem_store and Storage.new_local_filesystem. If we only kept Storage we could get rid of a lot of functions in favour of methods.

We decided to do this in #1179 (comment)_

[TomNicholas]

We actually have this problem for several classes:

1. Storage backends

• Remove in_memory_storage() in favour of Storage.new_in_memory()
• Remove local_filesystem_storage() in favour of Storage.new_local_filesystem()
• Remove s3_storage() in favour of Storage.new_s3()
• Remove gcs_storage() in favour of Storage.new_gcs()
• Remove azure_storage() in favour of Storage.new_azure_blob()
• Remove r2_storage() in favour of Storage.new_r2()
• Remove tigris_storage() in favour of Storage.new_tigris()

Note that in conjunction with #1179 then icechunk.r2_storage() will become icechunk.storage.Storage.new_r2() (or if we choose to keep Storage in the top-level namespace then icechunk.Storage.new_r2() will also work).

2. Storage configs

• Remove local_filesystem_store() in favour of ObjectStoreConfig.LocalFileSystem() (which should ideally be renamed to something like StoreConfig.localfilesystem())
• There doesn't appear to be an in_memory_store(), but there is a ObjectStoreConfig.InMemory() (which should ideally be renamed to something like StoreConfig.in_memory())
• Remove s3_store() in favour of ObjectStoreConfig.S3() (which should ideally be renamed to something like StoreConfig.s3())
• Remove gcs_store() in favour of ObjectStoreConfig.Gcs() (which should ideally be renamed to something like StoreConfig.gcs())
• There doesn't appear to be an azure_store(), but there is a ObjectStoreConfig.Azure() (which should ideally be renamed to something like StoreConfig.azure())
• Remove http_store() in favour of ObjectStoreConfig.Http() (which should ideally be renamed to something like StoreConfig.http())
• There doesn't appear to be an tigris_store(), but there is a ObjectStoreConfig.Tigris() (which should ideally be renamed to something like StoreConfig.tigris())

3. Credentials

These are so confusing that they should be discussed in a separate PR.

[mpiannucci]

I personally like the way it is now much better than what you have proposed, its much easier to use

[TomNicholas]

its much easier to use

Can you elaborate on why you find the current API easier to use? And are you saying you're in favour of keeping functions-as-contructors, or keeping two separate ways of constructing the same objects?

[mpiannucci]

I'm in favor of functions as constructors. It reads much more pythonic to me than having StoreConfig.some_storage(). I like that it's abstracted away to a verb, you create your s3 storage with this one function.

[TomNicholas]

it's abstracted away to a verb

There is no verb in the current functional API. You're suggesting a function named create_s3_storage()?

It reads much more pythonic to me than having StoreConfig.some_storage().

I feel like the more OOP approach is more "pythonic" 🤷 It's more similar to e.g. pathlib.Path.from_uri().

But the main reason I like Storage.{constructor} is because we should definitely add namespaces of some sort, so the functional approach would still look like icechunk.storage.{constructor}. If we're going to have an API like that we may as well make it icechunk.Storage.{constructor} and avoid the duplication of both functions and methods.