Deprecation: codify browndates for "no config file deprecation" (#10612)

* Deprecation: notification and feature flag for `build.image` config

Define a weekly task to communicate our users about the deprecation of
`build.image` using the deprecation plan we used for the configuration file v2
as well.

- 3 brownout days
- final removal date on October 2nd
- weekly onsite/email notification on Wednesday at 11:15 CEST (around 3.5k projects affected)
- allow to opt-out from these emails
- feature flag for brownout days
- build detail's page notification

Related:
* readthedocs/meta#48
* #10354
* #10587

* Deprecation: notification and feature flag for `build.image` config

Define a weekly task to communicate our users about the deprecation of
`build.image` using the deprecation plan we used for the configuration file v2
as well.

- 3 brownout days
- final removal date on October 2nd
- weekly onsite/email notification on Wednesday at 11:15 CEST (around ~22k projects affected)
- allow to opt-out from these emails
- feature flag for brownout days
- build detail's page notification

Related:
* readthedocs/meta#48
* #10354
* #10587

* Review and update logic

* Start emailing people with projects building from 3 years ago

* Apply suggestions from code review

Co-authored-by: Anthony <[email protected]>
Co-authored-by: Eric Holscher <[email protected]>

* Add HTML version of the email

* Codify brownout dates and remove the feature flag

Follows the suggestion from https://github.com/readthedocs/blog/pull/233/files#r1283479184

* Use UTC datetimes to compare

* Deprecation: codify browndates for "no config file deprecation"

Follows https://github.com/readthedocs/blog/pull/233/files#r1283479184

This way, we don't have to enable anything manually.
These dates are already communicated to users and will be automatically applied.

---------

Co-authored-by: Anthony <[email protected]>
Co-authored-by: Eric Holscher <[email protected]>

readthedocs/doc_builder/director.py

@@ -24,7 +24,6 @@
 from readthedocs.doc_builder.python_environments import Conda, Virtualenv
 from readthedocs.projects.constants import BUILD_COMMANDS_OUTPUT_PATH_HTML
 from readthedocs.projects.exceptions import RepositoryError
-from readthedocs.projects.models import Feature
 from readthedocs.projects.signals import after_build, before_build, before_vcs
 from readthedocs.storage import build_tools_storage
 
@@ -250,16 +249,24 @@ def checkout(self):
         self.data.build["config"] = self.data.config.as_dict()
         self.data.build["readthedocs_yaml_path"] = custom_config_file
 
+        now = timezone.now()
+
+        # fmt: off
+        # These browndates matches https://blog.readthedocs.com/use-build-os-config/
+        browndates = any([
+            timezone.datetime(2023, 7, 14, 0, 0, 0, tzinfo=timezone.utc) < now < timezone.datetime(2023, 7, 14, 12, 0, 0, tzinfo=timezone.utc),  # First, 12hs
+            timezone.datetime(2023, 8, 14, 0, 0, 0, tzinfo=timezone.utc) < now < timezone.datetime(2023, 8, 15, 0, 0, 0, tzinfo=timezone.utc),  # Second, 24hs
+            timezone.datetime(2023, 9, 4, 0, 0, 0, tzinfo=timezone.utc) < now < timezone.datetime(2023, 9, 6, 0, 0, 0, tzinfo=timezone.utc),  # Third, 24hs
+            timezone.datetime(2023, 9, 25, 0, 0, 0, tzinfo=timezone.utc) < now,  # Fully removal
+        ])
+        # fmt: on
+
         # Raise a build error if the project is not using a config file or using v1
-        if self.data.project.has_feature(
-            Feature.NO_CONFIG_FILE_DEPRECATED
-        ) and self.data.config.version not in ("2", 2):
+        if browndates and self.data.config.version not in ("2", 2):
             raise BuildUserError(BuildUserError.NO_CONFIG_FILE_DEPRECATED)
 
         # Raise a build error if the project is using "build.image" on their config file
 
-        now = timezone.now()
-
         # fmt: off
         # These browndates matches https://blog.readthedocs.com/use-build-os-config/
         browndates = any([

readthedocs/projects/models.py

@@ -1949,7 +1949,6 @@ def add_features(sender, **kwargs):
     # Build related features
     GIT_CLONE_FETCH_CHECKOUT_PATTERN = "git_clone_fetch_checkout_pattern"
     HOSTING_INTEGRATIONS = "hosting_integrations"
-    NO_CONFIG_FILE_DEPRECATED = "no_config_file"
     SCALE_IN_PROTECTION = "scale_in_prtection"
 
     FEATURES = (
@@ -2089,10 +2088,6 @@ def add_features(sender, **kwargs):
                 "Proxito: Inject 'readthedocs-addons.js' as <script> HTML tag in responses."
             ),
         ),
-        (
-            NO_CONFIG_FILE_DEPRECATED,
-            _("Build: Building without a configuration file is deprecated."),
-        ),
         (
             SCALE_IN_PROTECTION,
             _("Build: Set scale-in protection before/after building."),