cb04297420
Representing HTTP headers in a `java.util.Map` is error-prone, because the names (keys) need to be case-insensitive (per [RFC 2616 section 4.2](https://datatracker.ietf.org/doc/html/rfc2616#section-4.2)) but this is fundamentally technically incompatible with the `Map` interface (e.g. with headers `{"key": ["val_1", "val_2"]}` then `get("key")` and `get("KeY")` both return the same list, but `size()` returns `1`). It also breaks as soon as you copy the `Map` into a non-case-insensitive (i.e. normal) `Map` implementation, e.g. Guava's `ImmutableMap`. It's risky that a line as 'innocent' as `ImmutableMap.copyOf(headers)` could break things so badly. For now it's enough to keep this field unstable (it's currently the only reference to HTTP headers in the stable API). We can consider stabilising an improved HTTP header representation in future. PiperOrigin-RevId: 450708598
DataSource module
Provides a DataSource abstraction and a number of concrete implementations for
reading data from different sources. Application code will not normally need to
depend on this module directly.