GitHub Funding: Update all fields and add positive/negative tests (SchemaStore#4909)

* `otechie` is not a documented field as of 2025-08-12.
  It is now removed.

* `lfx_crowdfunding` is not a documented field as of 2025-08-12.
  It is now removed.

  Note that GitHub docs refer to the `community_bridge` field as
  "LFX Mentorship (formerly CommunityBridge)".

* GitHub's docs currently don't state that `null` is a valid value.
  Therefore, `null` is no longer a valid type for any supported field.

* External services' username length and pattern constraints
  do not appear to be documented by the external services
  and thus the existing schema constraints cannot be verified.
  Therefore, `maxLength` and `pattern` constraints are removed
  for `patreon`, `github`, and `polar`.

https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/displaying-a-sponsor-button-in-your-repository

Author: kurtmckee

src/negative_test/github-funding/buy_me_a_coffee-bad-type.json

@@ -0,0 +1,3 @@
+{
+  "buy_me_a_coffee": null
+}

src/negative_test/github-funding/buy_me_a_coffee-empty-string.json

@@ -0,0 +1,3 @@
+{
+  "buy_me_a_coffee": ""
+}

src/negative_test/github-funding/community_bridge-bad-type.json

@@ -0,0 +1,3 @@
+{
+  "community_bridge": null
+}

src/negative_test/github-funding/community_bridge-empty-string.json

@@ -0,0 +1,3 @@
+{
+  "community_bridge": ""
+}

src/negative_test/github-funding/custom-array-bad-format.json

@@ -0,0 +1,3 @@
+{
+  "custom": ["not a uri"]
+}

src/negative_test/github-funding/custom-array-bad-type.json

@@ -0,0 +1,3 @@
+{
+  "custom": [null]
+}

src/negative_test/github-funding/custom-array-not-unique.json

@@ -0,0 +1,3 @@
+{
+  "custom": ["https://example.com/1", "https://example.com/1"]
+}

src/negative_test/github-funding/custom-array-too-long.json

@@ -0,0 +1,9 @@
+{
+  "custom": [
+    "https://example.com/1",
+    "https://example.com/2",
+    "https://example.com/3",
+    "https://example.com/4",
+    "https://example.com/PROBLEM"
+  ]
+}

src/negative_test/github-funding/custom-array-too-short.json

@@ -0,0 +1,3 @@
+{
+  "custom": []
+}

src/negative_test/github-funding/custom-bad-type.json

@@ -0,0 +1,3 @@
+{
+  "custom": null
+}