Add concepts to docs

doc/crypt.adoc

@@ -50,6 +50,8 @@ include::crypt/hash_drbg.adoc[]
 
 include::crypt/hmac_drbg.adoc[]
 ////
+include::crypt/concepts.adoc[]
+
 include::crypt/config.adoc[]
 
 include::crypt/reference.adoc[]

doc/crypt/api_reference.adoc

@@ -101,6 +101,10 @@ https://www.boost.org/LICENSE_1_0.txt
 
 - None
 
+== Concepts
+
+- <<file_system_path, `file_system_path`>>
+
 == Macros
 
 See: <<configuration>>

doc/crypt/concepts.adoc

@@ -0,0 +1,51 @@
+////
+Copyright 2025 Matt Borland
+Distributed under the Boost Software License, Version 1.0.
+https://www.boost.org/LICENSE_1_0.txt
+////
+
+[#Concepts]
+= Concepts
+:idprefix: concepts_
+
+The following are the defintions of the concepts used throughout the library to ensure consistency.
+
+[#file_system_path]
+== File System Path
+
+Used for the one-shot hashing of files.
+Allows a diverse range of ways to specify the file path.
+This concept is disabled on CUDA because there is no `std::ifstream` on that platform.
+
+[source, c++]
+----
+namespace boost::crypt::concepts {
+
+#ifndef BOOST_CRYPT_HAS_CUDA
+
+template <typename T>
+concept file_system_path = std::is_convertible_v<T, std::string> ||
+                           std::is_convertible_v<T, std::string_view> ||
+                           std::is_same_v<std::remove_cvref<T>, std::filesystem::path>;
+
+#endif
+
+} // namespace boost::crypt::concepts
+----
+
+[#writable_output_range]
+== Writeable Output Range
+
+This concept is used to define the ranges that we can write to such as the `get_digest(Range&& data)` function of the hashers.
+
+[source, c++]
+----
+namespace boost::crypt::concepts {
+
+template <typename Range>
+concept writable_output_range = compat::output_range<Range, compat::range_value_t<Range>> &&
+                                compat::sized_range<Range> &&
+                                compat::is_trivially_copyable_v<compat::range_value_t<Range>>;
+
+} // namespace boost::crypt::concepts
+----