fix: fixing apns keys encoding

[geekbrother]

Description

To fix the multi-tenant apns update bug (where apns key is always wrong), the following changes and fixes are made:

Commit 163155f fix:

• Removing base64 encoding from the p8 key as it's in already base64 key format (PEM),
• Added missed decoding from base64 for the p12 key,
• Adding values extraction case when the password is not provided (key without password), as it was missed and always returning Invalid Multipart Body when the password was not provided,
• Replacing BufReader with Cursor as we don't need to create a buffer and can use just a cursor.

Commit 917c36a test:

• Functional unit test tenant_update_apns_valid_token was created to cover testing apns update using the reqwest post request with the multipart form with valid apns p8 key from the environment variable,
• Adding required CI variables passing to run tenant_update_apns_valid_token unit test with valid apns p8 key from GitHub secrets.

Resolves #244

How Has This Been Tested?

It was tested by the CI unit test tenant_update_apns_valid_token from this PR.
The expected behavior is passing the tenant_update_apns_valid_token from the CI gate.

Due Diligence

• Breaking change
• Requires a documentation update
• Requires a e2e/integration test update

[arein]

lgtm - tests are updated and I'm sure you thought through the migration path

Deferring to @chris13524

[geekbrother]

lgtm - tests are updated and I'm sure you thought through the migration path

API has not changed, so it doesn't require a migration from the current state except adding of few additional secrets (already done).

[flypaper0]

👏