Pass is_key_content_base64: true to app_store_connect_api_key

The DEVELOPER_KEY_CONTENT secret is stored base64-encoded, so fastlane
needs to be told to decode it before parsing. Matches the approach on
rewrite/v2. Removes the openssl-shell-out workaround from the previous
commits, which was solving the wrong problem.

fastlane/Fastfile

@@ -13,11 +13,10 @@
 # Uncomment the line if you want fastlane to automatically update itself
 # update_fastlane
 
-require 'tempfile'
-
 APP_NAME = ENV['APP_NAME']
 DEVELOPER_KEY_ID = ENV['DEVELOPER_KEY_ID']
 DEVELOPER_KEY_ISSUER_ID = ENV['DEVELOPER_KEY_ISSUER_ID']
+DEVELOPER_KEY_CONTENT = ENV['DEVELOPER_KEY_CONTENT']
 TEAM_ID = ENV['TEAM_ID']
 TEMP_KEYCHAIN_USER = ENV['TEMP_KEYCHAIN_USER']
 TEMP_KEYCHAIN_PASSWORD = ENV['TEMP_KEYCHAIN_PASSWORD']
@@ -25,27 +24,6 @@ DEVELOPER_APP_IDENTIFIER = ENV['DEVELOPER_APP_IDENTIFIER']
 GIT_AUTHORIZATION = ENV['GIT_AUTHORIZATION']
 TESTFLIGHT_EXTERNAL_GROUPS = ENV['TESTFLIGHT_EXTERNAL_GROUPS']
 
-# Ruby's OpenSSL bindings (via OpenSSL::PKey::EC.new in spaceship) raise
-# "invalid curve name" on the hosted macOS runners when given Apple's PKCS#8
-# .p8 key directly. Shelling out to the system openssl to emit SEC1/traditional
-# PEM sidesteps the issue. See fastlane/fastlane#20593.
-def developer_key_content
-  return @developer_key_content if defined?(@developer_key_content)
-  content = ENV['DEVELOPER_KEY_CONTENT']
-  return @developer_key_content = nil if content.nil? || content.empty?
-  # GitHub secrets carry multi-line PEMs as a single line with literal "\n"
-  # escapes; fastlane's action un-escapes these before use, so do the same
-  # here before invoking openssl.
-  content = content.gsub('\n', "\n")
-  @developer_key_content = Tempfile.open(['AuthKey', '.p8']) do |f|
-    f.write(content)
-    f.flush
-    converted = `openssl pkey -in #{f.path} -traditional 2>&1`
-    raise "Failed to convert P8 key: #{converted}" unless $?.success?
-    converted
-  end
-end
-
 XCODEPROJ = "#{APP_NAME}.xcodeproj"
 
 def delete_temp_keychain(name)
@@ -101,7 +79,8 @@ platform :ios do
     api_key = app_store_connect_api_key(
       key_id: DEVELOPER_KEY_ID,
       issuer_id: DEVELOPER_KEY_ISSUER_ID,
-      key_content: developer_key_content
+      key_content: DEVELOPER_KEY_CONTENT,
+      is_key_content_base64: true
     )
 
     build = get_build_number(xcodeproj: XCODEPROJ)
@@ -153,7 +132,8 @@ platform :tvos do
     api_key = app_store_connect_api_key(
       key_id: DEVELOPER_KEY_ID,
       issuer_id: DEVELOPER_KEY_ISSUER_ID,
-      key_content: developer_key_content
+      key_content: DEVELOPER_KEY_CONTENT,
+      is_key_content_base64: true
     )
 
     build = get_build_number(xcodeproj: XCODEPROJ)
@@ -205,7 +185,8 @@ platform :mac do
     api_key = app_store_connect_api_key(
       key_id: DEVELOPER_KEY_ID,
       issuer_id: DEVELOPER_KEY_ISSUER_ID,
-      key_content: developer_key_content
+      key_content: DEVELOPER_KEY_CONTENT,
+      is_key_content_base64: true
     )
 
     build = get_build_number(xcodeproj: XCODEPROJ)
@@ -256,7 +237,8 @@ platform :mac do
     api_key = app_store_connect_api_key(
       key_id: DEVELOPER_KEY_ID,
       issuer_id: DEVELOPER_KEY_ISSUER_ID,
-      key_content: developer_key_content
+      key_content: DEVELOPER_KEY_CONTENT,
+      is_key_content_base64: true
     )
 
     build = get_build_number(xcodeproj: XCODEPROJ)