Create README.md

README.md

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+# Allows to have a dynamic authority at runtime
+
+With the help of changing the JwtHandler by a service, that allows you to define the openidconfiguration/multiple ones at runtime.
+
+
+# How to use
+
+> Startup class
+
+```csharp
+ public class Startup
+    {
+        private readonly IConfiguration configuration;
+
+        public Startup(IConfiguration configuration)
+        {
+            this.configuration = configuration;
+        }
+
+
+        // This method gets called by the runtime. Use this method to add services to the container.
+        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
+        public void ConfigureServices(IServiceCollection services)
+        {
+            services.AddHttpContextAccessor();
+            services.AddMemoryCache();
+            services
+                .AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
+                .AddDynamicJwtBearer(JwtBearerDefaults.AuthenticationScheme, options =>
+                {
+                    options.TokenValidationParameters.ValidateAudience = false;
+                })
+                .AddDynamicAuthorityJwtBearerResolver<ResolveAuthorityService>();
+
+            services.AddControllers();
+        }
+
+        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
+        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
+        {
+
+            if (env.IsDevelopment())
+            {
+                app.UseDeveloperExceptionPage();
+            }
+
+            app.UseRouting();
+            app.UseAuthentication();
+            app.UseAuthorization();
+            app.UseEndpoints(endpoints =>
+            {
+                endpoints.MapControllers();
+            });
+        }
+    }
+```
+
+> Simple authority resolver with header X-Tenant
+
+```csharp
+internal class ResolveAuthorityService : IDynamicJwtBearerAuthorityResolver
+    {
+        private readonly IConfiguration configuration;
+
+        public ResolveAuthorityService(IConfiguration configuration)
+        {
+            this.configuration = configuration;
+        }
+
+        public TimeSpan ExpirationOfConfiguration => TimeSpan.FromHours(1);
+
+        public Task<string> ResolveAuthority(HttpContext httpContext)
+        {
+            var realm = httpContext.Request.Headers["X-Tenant"].FirstOrDefault() ?? configuration["KeyCloak:MasterRealm"];
+            var authority = $"{configuration["KeyCloak:Endpoint"]}/realms/{realm}";
+            return Task.FromResult(authority);
+        }
+    }
+```